An ornamental plant escapes into Lake Victoria and chokes it, while the women who smoke the lake's fish breathe in woodsmoke and walk miles for firewood. A village project mixes the weed with cow dung to make clean cooking gas. It works, but the machines cost more than most villages can pay.
The TRUE / FALSE / NOT GIVEN block (1-7) covers paragraphs B to D. The flow-chart (8-10) is all paragraphs F and G. The notes (11-13) come from H and J.
TRUE / FALSE / NOT GIVEN
Questions 1-7
How to attack this block: In order, with two NOT GIVENs that both ask you to go one step further than the passage: a cause for falling fish numbers, and a health ranking of charcoal against wood. The passage mentions both topics but never makes either claim.
Question 1
Answer: TRUEParagraph B, first sentence
Was water hyacinth brought to east Africa because it looked nice?
In east Africa the plant arrived with Belgian colonists in Rwanda, who liked the look of its glossy leaves and delicate purple flowers floating in their ponds.
Question says → Passage says
introducedarrived with Belgian colonists
as a decorative plantliked the look of its glossy leaves and delicate purple flowers floating in their ponds
Why: The colonists brought it because they liked how it looked and kept it in their ponds. A plant kept for its looks is a decorative plant, so TRUE.
The trap: Paragraph A says it spread from the southern tip of Africa, which might suggest it wasn't 'introduced' to east Africa at all. But B is specifically about east Africa, and there it came with the colonists.
Question 2
Answer: FALSEParagraph B, second sentence
Did fishermen carry the plant to Lake Victoria?
it had 'escaped' out of the country via the Kagera river and made its way downstream to Lake Victoria
Question says → Passage says
took some plants to Lake Victoriamade its way downstream to Lake Victoria
Why: The plant got to the lake on its own, by floating down the Kagera river. Nobody carried it there, so the statement contradicts the passage: FALSE.
The trap: NOT GIVEN is tempting because fishermen aren't mentioned in this sentence. But the passage tells you exactly how the plant arrived, and that rules out people taking it. Fishermen only appear later as victims of the weed.
Question 3
Answer: TRUEParagraph C, first sentence
Is it now hard for boats to get through the hyacinth on the lake?
the boats that once brought the fish to shore by the hundreds struggle to navigate through the mass of plants
Question says → Passage says
it is now difficult to force boats throughstruggle to navigate through
the thick water hyacinththe mass of plants
Why: 'Struggle to navigate through' means it's hard to get through, and 'the mass of plants' is the thick hyacinth. TRUE.
Question 4
Answer: NOT GIVENParagraph B, last sentence
Are chemicals from the plant reducing fish numbers in the lake?
blocking fishing routes and providing a new habitat for disease-carrying mosquitoes
Question says → Passage says
affecting fishblocking fishing routes
Why: The passage says the plant blocks fishing routes and makes it hard for boats to land fish, which hurts the women's income. It never mentions chemicals from the plant or any effect on fish numbers. NOT GIVEN.
The trap: Declining income for fish sellers can look like fewer fish. The passage blames boats struggling through the weed, not a drop in fish population.
Question 5
Answer: NOT GIVENParagraph C, last three sentences
Has charcoal been proved worse for health than wood?
About three out of four families in Kenya depend on wood or charcoal to cook their daily meals… Using solid fuels like these for cooking increases indoor pollution.
Question says → Passage says
cooking with charcoal… cooking with wooddepend on wood or charcoal to cook
worse for people's healthincreases indoor pollution
Why: Wood and charcoal are always grouped together as 'solid fuels' that cause indoor pollution. The passage never compares the two, so NOT GIVEN.
The trap: The WHO figure of 14,300 deaths a year sounds like proof of something. It's about indoor air pollution in general, not charcoal versus wood.
Question 6
Answer: FALSEParagraph D, first sentence
Were people unable to take much hyacinth out of the lake?
huge piles of water hyacinth that villagers had taken out of the water in an attempt to clear it were a common sight
Question says → Passage says
peoplevillagers
found it impossible to remove muchhuge piles of water hyacinth that villagers had taken out of the water
Why: Villagers took out enough to make 'huge piles', and these were 'a common sight'. That's a lot of hyacinth removed, which contradicts 'impossible to remove much'. FALSE.
The trap: 'In an attempt to clear it' suggests they didn't manage to clear the lake completely. That's true, but the statement says they couldn't remove much, and huge piles prove they did.
Question 7
Answer: TRUEParagraph D, fourth sentence
Did scientists start looking at hyacinth as a biofuel source in the 20th century?
a magic combination that has captivated researchers' imaginations since as early as the 1980s when, across the world, they began to explore its potential as a biofuel
Question says → Passage says
scientists started investigatingresearchers… began to explore
the possibility of using water hyacinth to generate biogasits potential as a biofuel
in the last centuryas early as the 1980s
Why: The 1980s were in the 20th century, which is 'the last century'. Exploring its 'potential as a biofuel' is investigating whether it could produce fuel gas. TRUE.
The trap: Some people only notice the 2014 Nigerian research and the 2018 Dunga project, which are this century. The research started much earlier.
Flow-chart completion (NO MORE THAN TWO WORDS)
Questions 8-10
How to attack this block: Two words are allowed here, and question 8 needs both. The steps follow the stomach comparison in G: what goes in, what happens inside, how the gas leaves. Earlier paragraphs mention a different kind of manure, so be sure you're reading the Dunga project.
Question 8
Answer: cow dungParagraph F, last sentence
What is mixed with the water hyacinth in the digester?
machines that would transform a mix of water hyacinth and cow dung into biogas for cooking
Question says → Passage says
place water hyacinth together witha mix of water hyacinth and
a digesterbiogas digesters
Why: Dunga's digesters take 'a mix of water hyacinth and cow dung'. Two words are allowed, and 'cow dung' is the exact phrase.
The trap: 'Chicken manure' is in paragraph E, but that was the Nigerian experiment. The flow chart is about Dunga, and Dunga uses cow dung.
Question 9
Answer: fermentationParagraph G, second sentence
Also accepted: fermentation process
What process do you wait for before the gas comes out?
over the next 20 to 30 days, it goes through a fermentation process and breaks down, giving off gas
Question says → Passage says
leave the mixture untilover the next 20 to 30 days
is completedgoes through… and breaks down
Why: The mixture sits for 20 to 30 days while it ferments. The gap follows 'the' and takes 'is completed', so it needs a noun: 'fermentation', or 'fermentation process', which is still within two words.
The trap: Don't write 'breaks down': it's a verb, and 'until the breaks down is completed' isn't English.
Question 10
Answer: pipesParagraph G, third sentence
What carries the gas to people's homes?
the clean-burning gas is passed through pipes to the point of use, just like traditional domestic gas
Question says → Passage says
transport itis passed through
to individual homesto the point of use / domestic
Why: The gas goes 'through pipes' to where it's used. The gap follows 'use' and needs a plural noun: 'pipes'.
The trap: 'Stoves' appear in the next sentences, but stoves are where the gas is burnt, not how it travels.
Note completion (ONE WORD ONLY)
Questions 11-13
How to attack this block: The benefits come from H and the drawback from J. All three answers are plain everyday nouns. The only risk is writing a longer phrase from the passage when the notes allow one word.
Question 11
Answer: timeParagraph H, fourth sentence
What don't the women need to spend so much of collecting fuel?
they don't have to devote a lot of time every day to gathering firewood
Question says → Passage says
no need for them to spend so muchdon't have to devote a lot of
collecting fuelgathering firewood
Why: 'Devote time' becomes 'spend time', and 'gathering firewood' is 'collecting fuel'. One word: 'time'.
The trap: 'Energy' or 'effort' feel natural with 'spend', and paragraph C mentions walking 10km. But the word in paragraph H is 'time', and you must take the word from the passage.
Question 12
Answer: moneyParagraph H, last sentence
What do their other activities bring in?
they're able to make more money for their families from other enterprises
Question says → Passage says
focus on different tasksother enterprises
bring inmake more
Why: 'Other enterprises' are the different tasks, and what they bring in is money. One word, so 'money', not 'more money'.
The trap: 'Income' is the passage's word in paragraph C, but that was income lost from fish smoking. The benefit here is worded as 'money'.
Question 13
Answer: priceParagraph J, last sentence
What about the digesters is too much for most villages?
But unless the price of the machines drops, it's pretty clear that most communities will never be able to afford any, since they sell for about $750.
Question says → Passage says
the digestersthe machines
beyond the reach of most villagesmost communities will never be able to afford any
Why: 'Beyond the reach' here means too expensive, and the passage blames 'the price of the machines'. The gap follows 'the' and comes before 'of the digesters', so it needs a noun: 'price'.
The trap: 'Affordability' appears in paragraph K, but 'the affordability of the digesters is beyond the reach' doesn't make sense. You also can't write '$750' as one word that fits the grammar.
The Nigerian research (E) used chicken manure. The Dunga digesters (F) take cow dung. The flow-chart is about Dunga, so the answer is cow dung, and it needs both words.
Paragraph C groups wood and charcoal together as solid fuels. It never ranks one above the other, so NOT GIVEN.
Words from this passage worth keeping
obstruct(A)
block something so it can't work or move freely
headache(C)
a problem that causes worry (informal)
foliage(D)
the leaves of a plant
captivate(D)
hold someone's attention and interest strongly
menace(F)
something dangerous or harmful
fermentation(G)
a chemical breakdown caused by bacteria or yeast
devote(H)
give time or effort to a particular activity
respiratory(I)
to do with breathing and the lungs
Sit this test on Langujet, then come back
The full Cambridge 21 Test 4 reading paper: all three passages, 60 minutes, marked the second you finish with a review of every answer. Already done it? Take it again and see if the same traps still get you.
Cambridge IELTS 21, Test 4, Reading Passage 1. The passage and questions belong to Cambridge University Press and are not reproduced here. We quote short extracts only as evidence for our own commentary, and the answers are published for self-marking. Get the book for the full text, or sit the test on Langujet.
FAQ
The problems and benefits created by the spread of the water hyacinth in Kenya: quick answers
"The problems and benefits created by the spread of the water hyacinth in Kenya" is Reading Passage 1 of Cambridge IELTS 21, Test 4. It covers questions 1-13 (13 marks).
Questions 1-7: TRUE / FALSE / NOT GIVEN, questions 8-10: Flow-chart completion and questions 11-13: Note completion.
3 TRUE, 2 FALSE and 2 NOT GIVEN.
Our review highlights questions 8, 6 and 5. Each one is explained in "Questions worth a second look" above.
The rest of Cambridge 21 Test 4
Passage 1 · Questions 1-13 · You're hereThe problems and benefits created by the spread of the water hyacinth in Kenya
