Cambridge 21 Test 4 Reading Answers & Explanations

This post provides the complete answers and clear explanations for Cambridge IELTS 21 Academic Reading Test 4.

Each answer includes:

• Strategy
• Keywords
• Exact paragraph and line location
• Explanation
• Correct answer

> Location note: Line numbers are counted within each paragraph as displayed in the reading passage. When a paragraph continues onto the next page, the line count continues.

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Reading Passage 1

The Problems and Benefits Created by the Spread of the Water Hyacinth in Kenya

Questions 1–7: TRUE, FALSE, NOT GIVEN

Strategy

For this question type:

• Choose TRUE when the statement agrees with the passage.
• Choose FALSE when the passage gives opposite information.
• Choose NOT GIVEN when the passage does not provide enough information.

Always compare the complete meaning instead of matching keywords only.

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Question 1

Water hyacinth was introduced as a decorative plant in east Africa.

Keywords

water hyacinth, introduced, decorative plant, east Africa

Location + Explanation

Reading Passage 1, Paragraph 2, lines 1–2

The passage explains that Belgian colonists brought the plant to Rwanda because they liked its glossy leaves and purple flowers.

Here:

• liked its appearance = decorative purpose
• arrived with Belgian colonists = was introduced by them

The statement agrees with the passage.

So, the answer is: TRUE

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Question 2

Fishermen took some water hyacinth plants to Lake Victoria.

Keywords

fishermen, took plants, Lake Victoria

Location + Explanation

Reading Passage 1, Paragraph 2, lines 2–3

The plant escaped from Rwanda through the Kagera River and moved downstream to Lake Victoria.

Here:

• escaped through the river is different from taken by fishermen

The statement gives the wrong explanation.

So, the answer is: FALSE

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Question 3

It is now difficult to force boats through the thick water hyacinth on Lake Victoria.

Keywords

difficult, boats, thick water hyacinth, Lake Victoria

Location + Explanation

Reading Passage 1, Paragraph 3, lines 1–3

The passage says boats struggle to navigate through the mass of plants.

Here:

• struggle to navigate = find it difficult to move
• mass of plants = thick water hyacinth

The statement matches the passage.

So, the answer is: TRUE

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Question 4

Chemicals produced by water hyacinth plants are affecting the numbers of fish in Lake Victoria.

Keywords

chemicals, fish numbers, water hyacinth

Location + Explanation

Closest related location: Reading Passage 1, Paragraph 2, lines 3–5

The passage mentions blocked fishing routes and disease-carrying mosquitoes.

However, it does not mention:

• chemicals produced by the plant;
• chemicals affecting fish;
• changes in fish numbers.

The required information is missing.

So, the answer is: NOT GIVEN

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Question 5

Cooking with charcoal has been proved to be even worse for people’s health than cooking with wood.

Keywords

charcoal, worse than wood, health

Location + Explanation

Closest related location: Reading Passage 1, Paragraph 4, lines 1–5

The passage says both wood and charcoal increase indoor air pollution.

However, it does not compare the two fuels or say that charcoal is more harmful.

Here:

• Both fuels are harmful.
• No comparison is provided.

So, the answer is: NOT GIVEN

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Question 6

People found it impossible to remove much water hyacinth from Lake Victoria.

Keywords

impossible, remove, water hyacinth

Location + Explanation

Reading Passage 1, Paragraph 5, lines 1–2

The passage describes huge piles of water hyacinth that villagers had removed from the lake.

Here:

• huge piles were removed contradicts impossible to remove much

So, the answer is: FALSE

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Question 7

Scientists started investigating the possibility of using water hyacinth to generate biogas in the last century.

Keywords

scientists, investigating, biogas, last century

Location + Explanation

Reading Passage 1, Paragraph 5, lines 4–6

Researchers began exploring the plant’s potential as a biofuel in the 1980s.

Here:

• exploring its potential = investigating the possibility
• 1980s = last century

So, the answer is: TRUE

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Questions 8–10: Flow-Chart Completion

Strategy

For flow-chart questions:

1. Read the title of the process.
2. Identify the action words.
3. Locate the paragraph describing the process.
4. Follow the steps in order.
5. Check the word limit.

The instruction says:

Choose NO MORE THAN TWO WORDS from the passage for each answer.

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Question 8

Place water hyacinth together with some ______ into a digester.

Keywords

water hyacinth, together with, digester

Location + Explanation

Reading Passage 1, Paragraph 7, lines 3–4

The digesters transform a mixture of water hyacinth and cow dung into biogas.

Here:

• a mix of water hyacinth and cow dung = water hyacinth together with cow dung

So, the answer is: cow dung

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Question 9

Leave the mixture until the ______ is completed.

Keywords

mixture, completed, 20 to 30 days

Location + Explanation

Reading Passage 1, Paragraph 8, lines 1–3

The mixture remains inside the digester for 20 to 30 days while it goes through a fermentation process.

Here:

• The mixture is left until the fermentation process is complete.

So, the answer is: fermentation process

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Question 10

Use ______ to transport the gas to individual homes.

Keywords

gas, transport, homes

Location + Explanation

Reading Passage 1, Paragraph 8, lines 3–4

The clean-burning gas is passed through pipes to the place where it will be used.

Here:

• passed through pipes = transported using pipes

So, the answer is: pipes

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Questions 11–13: Note Completion

Strategy

For note-completion questions:

1. Read the heading and surrounding notes.
2. Decide what type of word is needed.
3. Locate the related information.
4. Copy the exact word from the passage.
5. Follow the word limit.

The instruction says:

Choose ONE WORD ONLY from the passage for each answer.

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Question 11

The women do not need to spend so much ______ collecting fuel.

Keywords

women, spend, collecting fuel

Location + Explanation

Reading Passage 1, Paragraph 9, lines 3–4

The women no longer need to devote a lot of time to gathering firewood.

Here:

• devote a lot of time = spend so much time
• gathering firewood = collecting fuel

So, the answer is: time

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Question 12

They can focus on different tasks that bring in ______.

Keywords

different tasks, bring in, enterprises

Location + Explanation

Reading Passage 1, Paragraph 9, lines 4–5

The passage says the women can earn more money through other enterprises.

Here:

• different tasks = other enterprises
• bring in = earn or make

So, the answer is: money

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Question 13

The ______ of the digesters is beyond the reach of most villages.

Keywords

digesters, beyond reach, afford

Location + Explanation

Reading Passage 1, Paragraph 11, lines 1–4

The digesters cost approximately $750, and most communities cannot afford them.

Here:

• cannot afford the machines = their price is beyond reach

So, the answer is: price

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Reading Passage 2

How Could Multilingualism Benefit India’s Poorest Schoolchildren?

Questions 14–19: Summary Completion

Strategy

For summary completion with a word list:

1. Read the complete summary.
2. Decide what type of word is needed.
3. Locate the related paragraph.
4. Match synonyms and paraphrases.
5. Check that the answer fits grammatically.

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Question 14

The city of Delhi has a ______.

Keywords

Delhi, population, people

Location + Explanation

Reading Passage 2, Paragraph 1, lines 1–3

The passage describes crowded streets and says more than 20 million people live in Delhi.

Here:

• more than 20 million people = dense population

So, the answer is: I — dense population

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Question 15

Some people have spent their entire lives in Delhi, while others are ______.

Keywords

entire lives, recently moved, Delhi

Location + Explanation

Reading Passage 2, Paragraph 1, lines 3–5

The passage contrasts people born in Delhi with millions who have recently moved there.

Here:

• recently made Delhi their home = new immigrants

So, the answer is: J — new immigrants

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Question 16

Whether they have come from a ______ or travelled from the other side of India...

Keywords

surrounding neighbourhood, other side of India

Location + Explanation

Reading Passage 2, Paragraph 1, lines 3–5

The passage says some people moved from surrounding neighbourhoods, cities and states.

Here:

• surrounding neighbourhood = nearby district

So, the answer is: H — nearby district

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Question 17

They have come in search of improved ______.

Keywords

search, improved, better jobs

Location + Explanation

Reading Passage 2, Paragraph 1, lines 4–5

Many people move to Delhi hoping to find better jobs and a better life.

Here:

• better jobs = improved employment opportunities

So, the answer is: B — employment opportunities

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Question 18

The ______ of the research is to discover why...

Keywords

research, aim, discover why

Location + Explanation

Reading Passage 2, Paragraph 2, lines 1–4

The passage describes the overriding aim of the four-year research project.

Here:

• overriding aim = primary objective

So, the answer is: E — primary objective

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Question 19

Multilingual Indian schoolchildren do not experience ______ to those experienced by multilingual children in Europe.

Keywords

multilingual children, benefits, Europe

Location + Explanation

Reading Passage 2, Paragraph 2, lines 3–7

The passage says Indian children do not experience the benefits of multilingualism observed in European schools.

Here:

• benefits = advantages
• the same benefits = similar advantages

So, the answer is: F — similar advantages

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Questions 20–23: YES, NO, NOT GIVEN

Strategy

• Choose YES when the statement agrees with the writer.
• Choose NO when the statement contradicts the writer.
• Choose NOT GIVEN when there is not enough information.

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Question 20

Ten-year-old Indian schoolchildren tend to perform better in literacy tests than in numeracy tests.

Keywords

ten-year-olds, literacy, numeracy, better

Location + Explanation

Reading Passage 2, Paragraph 3, lines 1–3

The passage says:

• More than 50% cannot complete the reading task fluently.
• Just under 50% cannot complete the subtraction task.

A slightly higher percentage struggles with literacy.

Therefore, literacy performance is slightly worse, not better.

So, the answer is: NO

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Question 21

Tsimpli had problems convincing some female students to take part in the study.

Keywords

Tsimpli, female students, take part

Location + Explanation

Closest related location: Reading Passage 2, Paragraph 3, lines 3–5

The passage says female students are more seriously affected by school dropout.

However, it does not mention:

• convincing girls to participate;
• girls refusing to participate;
• problems recruiting students.

So, the answer is: NOT GIVEN

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Question 22

Tsimpli and her team wanted to know if poor academic performance was connected to being taught in an unfamiliar language.

Keywords

poor performance, unfamiliar language, connection

Location + Explanation

Reading Passage 2, Paragraph 4, lines 1–3

The researchers are investigating whether low learning outcomes are caused by children being taught in a language different from the one used at home.

Here:

• low learning outcomes = poor academic performance
• different from the home language = unfamiliar language

So, the answer is: YES

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Question 23

The researchers decided against investigating the impact of teaching methods on learning outcomes.

Keywords

decided against, teaching methods, learning outcomes

Location + Explanation

Reading Passage 2, Paragraph 5, lines 1–5

The researchers intend to examine teaching practices and the lack of pupil-centred teaching.

The statement says they decided not to investigate these issues, which is the opposite of the passage.

So, the answer is: NO

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Questions 24–26: Multiple Choice

Strategy

For multiple-choice questions:

1. Find the relevant paragraph.
2. Read the complete paragraph.
3. Identify its main idea.
4. Compare all four options.
5. Eliminate unsupported answers.

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Question 24

What point does the writer make about primary schools in India in the sixth paragraph?

Keywords

primary schools, English instruction, poor children

Location + Explanation

Reading Passage 2, Paragraph 6, lines 1–6

The passage says English-medium instruction may hold back children who have little familiarity with English, especially those from low socio-economic backgrounds.

Here:

• may hold back = may disadvantage
• low socio-economic areas = poor backgrounds
• English as the medium of instruction = instructed in English

So, the answer is: C — Poor children may be disadvantaged further by being instructed in English.

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Question 25

What does Tsimpli mean by the phrase “that ship has sailed”?

Keywords

that ship has sailed, English, withdrawn

Location + Explanation

Reading Passage 2, Paragraph 7, lines 1–7; key phrase in lines 4–5

Tsimpli says English should not necessarily be the main teaching language, but she is not suggesting its complete removal.

The expression means the opportunity to make that change has already passed.

So, the answer is: D — It is too late to remove English completely as a language of instruction in schools.

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Question 26

What finding surprised the researchers?

Keywords

surprised, researchers, slum children

Location + Explanation

Reading Passage 2, Paragraph 8, lines 1–4

The surprising finding was that children from slum backgrounds did not perform worse than children from other poor urban backgrounds.

In some literacy and numeracy tasks, they performed better.

Here:

• unanticipated finding = surprising result
• do not lag behind = their skills are not lower

So, the answer is: D — The literacy and numeracy skills of slum children are not lower than those of children from other urban poor backgrounds.

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Reading Passage 3

The Globemakers: The Curious Story of an Ancient Craft

Questions 27–32: Summary Completion

Strategy

For summary-completion questions:

1. Read the summary heading.
2. Locate the relevant paragraphs.
3. Identify the type of word needed.
4. Match paraphrases.
5. Check grammar and meaning.

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Question 27

Peter Bellerby’s plan to give his father a globe was an unexpectedly ______.

Keywords

Bellerby, father, globe, unexpectedly

Location + Explanation

Reading Passage 3, Paragraph 1, lines 1–4

What appeared to be a simple plan became a difficult journey lasting around a decade.

Here:

• seemed simple but became difficult = challenging task

So, the answer is: G — challenging task

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Question 28

He had to overcome ______.

Keywords

overcome, obstacles, problems

Location + Explanation

Reading Passage 3, Paragraph 1, lines 2–4

The journey was marked by a series of obstacles.

Here:

• series of obstacles = numerous problems

So, the answer is: J — numerous problems

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Question 29

A straightforward ______ would not be possible.

Keywords

straightforward, online order, purchase

Location + Explanation

Reading Passage 3, Paragraph 2, lines 1–3

The passage says obtaining a suitable globe was not simply a matter of making a quick online order.

Here:

• quick online order = internet purchase

So, the answer is: I — internet purchase

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Question 30

Some ______ were available.

Keywords

available, shoddy commercial versions

Location + Explanation

Reading Passage 3, Paragraph 3, lines 1–2

Bellerby found poorly made commercial globes designed for classrooms.

Here:

• shoddy commercial versions = inferior makes

So, the answer is: C — inferior makes

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Question 31

The commercial globes had been intended for ______.

Keywords

intended for, school classrooms

Location + Explanation

Reading Passage 3, Paragraph 3, lines 1–2

The commercial globes were designed for school classrooms.

Here:

• designed for classrooms = intended for educational use

So, the answer is: A — educational use

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Question 32

He travelled to places where people might still have the ______.

Keywords

travelled, Morocco, India, cartographers, knowledge

Location + Explanation

Reading Passage 3, Paragraph 3, lines 2–4

Bellerby travelled to Morocco and India hoping to find people who had preserved the knowledge of artisan cartographers.

Here:

• specialist knowledge = necessary skills

So, the answer is: E — necessary skills

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Questions 33–36: YES, NO, NOT GIVEN

Strategy

• Choose YES when the statement agrees with the writer.
• Choose NO when the passage gives the opposite claim.
• Choose NOT GIVEN when the required information is missing.

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Question 33

The assumption that people in the past knew very little about geography is correct.

Keywords

assumption, people in the past, geography

Location + Explanation

Reading Passage 3, Paragraph 2, lines 2–4

The passage says the popular belief in ancient geographical ignorance is contrary to the evidence.

People have known the world is spherical since at least the sixth century BCE.

The writer therefore rejects the assumption.

So, the answer is: NO

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Question 34

Plato was criticised for saying the world was shaped like a leather ball.

Keywords

Plato, criticised, leather ball

Location + Explanation

Closest related location: Reading Passage 3, Paragraph 2, lines 4–5

The passage says Plato compared the world to a leather ball.

However, it does not mention:

• whether anyone criticised him;
• how people reacted;
• whether the comparison was controversial.

So, the answer is: NOT GIVEN

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Question 35

The globe made by Crates of Mallus accurately represented the known world.

Keywords

Crates of Mallus, globe, accurate

Location + Explanation

Closest related location: Reading Passage 3, Paragraph 2, lines 5–7

The passage says Crates of Mallus made the first recorded globe around 150 BCE.

However, it gives no information about the globe’s accuracy.

So, the answer is: NOT GIVEN

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Question 36

Bellerby expected to have few problems locating a well-made globe.

Keywords

Bellerby, few problems, well-made globe

Location + Explanation

Reading Passage 3, Paragraph 2, lines 7–8

Bellerby believed that a good-quality globe would not be difficult to find.

Here:

• would not be difficult = expected few problems
• good-quality globe = well-made globe

So, the answer is: YES

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Questions 37–40: Multiple Choice

Strategy

1. Locate the relevant paragraph.
2. Read the complete section.
3. Identify the main point.
4. Compare it with every option.
5. Eliminate options that add unsupported information.

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Question 37

What happened when Bellerby attached the gores to the globe surface?

Keywords

attach gores, globe surface, paper, problem

Location + Explanation

Reading Passage 3, Paragraph 5, lines 6–11; key information in lines 8–10

Near the end of the process, Bellerby discovered that the paper had stretched. The final gore therefore overlapped the first one.

Here:

• paper had stretched = unexpected problem
• final gore overlapped the first = result of the problem

So, the answer is: B — He became aware of an unexpected issue.

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Question 38

Why does the reviewer mention other globemakers from the past?

Keywords

reviewer, globemakers, past, Bellerby

Location + Explanation

Reading Passage 3, Paragraph 6, lines 1–11

The reviewer discusses Martin Behaim and Vincenzo Coronelli.

Bellerby shared qualities and experiences with them:

• Like Behaim, he faced unexpected difficulties.
• Like Coronelli, he showed strong ambition and determination.

So, the answer is: C — Bellerby had something in common with each of them.

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Question 39

What point is made about Bellerby in the seventh paragraph?

Keywords

Bellerby, traditional skills, craftsmen

Location + Explanation

Reading Passage 3, Paragraph 7, lines 1–7

The passage describes the book as a lament for disappearing traditions.

Bellerby struggled to find skilled craftspeople, and many of those he eventually found have retired or died.

Here:

• lament for fading traditions = regret about their disappearance
• craftspeople retiring or dying = loss of specialist skills

So, the answer is: D — He regrets the loss of many globe-making skills.

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Question 40

What does the reviewer say about Bellerby’s book in the final paragraph?

Keywords

reviewer, book, final paragraph, commercial success

Location + Explanation

Reading Passage 3, Paragraph 8, lines 4–6

The reviewer says the book is not a blueprint for commercial success.

A blueprint means a detailed guide or plan.

Therefore, the book does not explain how to establish a profitable company. Instead, it creates admiration for traditional craftsmanship and Bellerby’s determination.

So, the answer is: A — It does not tell you how to create a profitable business.

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Cambridge 21 Test 4 Reading Answer Key

Reading Passage 1

1. TRUE
2. FALSE
3. TRUE
4. NOT GIVEN
5. NOT GIVEN
6. FALSE
7. TRUE
8. cow dung
9. fermentation process
10. pipes
11. time
12. money
13. price

Reading Passage 2

14. I — dense population
15. J — new immigrants
16. H — nearby district
17. B — employment opportunities
18. E — primary objective
19. F — similar advantages
20. NO
21. NOT GIVEN
22. YES
23. NO
24. C
25. D
26. D

Reading Passage 3

27. G — challenging task
28. J — numerous problems
29. I — internet purchase
30. C — inferior makes
31. A — educational use
32. E — necessary skills
33. NO
34. NOT GIVEN
35. NOT GIVEN
36. YES
37. B
38. C
39. D
40. A

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Bonus IELTS Reading Tips

Follow the Word Limit

Always check whether the instruction says:

• ONE WORD ONLY
• NO MORE THAN TWO WORDS
• NO MORE THAN THREE WORDS

Writing more words than allowed will make the answer incorrect.

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Look for Paraphrases

Question wording	Passage wording
decorative plant	liked the appearance of its leaves and flowers
difficult to move through	struggle to navigate
thick water hyacinth	mass of plants
collecting fuel	gathering firewood
bring in money	make more money
employment opportunities	better jobs
primary objective	overriding aim
numerous problems	series of obstacles
internet purchase	quick online order
inferior makes	shoddy commercial versions
necessary skills	knowledge of artisan cartographers

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Understand FALSE and NOT GIVEN

Choose FALSE when the passage gives opposite information.

Choose NOT GIVEN when the passage does not provide enough information.

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Be Careful with Comparison Words

Words such as these can change the meaning of a statement:

• better
• worse
• more
• less
• higher
• lower
• most
• only
• always
• never

For example, the passage says wood and charcoal are harmful, but it does not say which is worse.

Therefore, the answer is NOT GIVEN.

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Follow the Order of the Passage

Most IELTS Reading questions follow the order of the information.

After locating one answer, continue reading from that point instead of returning to the beginning.

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Check Grammar

The answer must fit naturally into the incomplete sentence.

For example:

> The price of the digesters is beyond the reach of most villages.

The word price fits both the grammar and meaning.