This natural rubber lecture listening test page closes Cambridge IELTS 21 Listening Test 1 with Section 4: the complete answer key for Questions 31–40, playable audio, an explanation for every question with the exact transcript line that proves it, and the full recording script. One speaker delivers an unbroken lecture on the natural resources industry depends on, and all ten questions are note completion with a strict ONE WORD ONLY limit.

The talk signposts its own structure — essential resources, the limits on rubber supply, new threats, synthetic rubber, then dandelions as an alternative source — and the ten answers arrive in that order without a pause. Read the notes ahead of the audio with the note completion strategy and fix the word class of every gap, then confirm your marks on the complete Cambridge IELTS 21 Listening Test 1 answers page, which covers all four sections of the paper.

Listening Audio — Section 4

Play the recording once, without pausing, and answer Questions 31–40 before you check the key. In the real exam you hear each section exactly once.

Questions 31–40

Questions 31–40

Complete the notes below.

Write ONE WORD ONLY for each answer.

Three resources which are essential for industrial civilisation

This mainly comes from the Pará rubber tree, now cultivated in South-East Asia. The supply is limited because

• Sources of rubber
• 31 …………
• fossil fuels
• rubber
• Natural rubber
• the growth of the tree is 32 ………… .
• production cannot easily be adjusted because of increasing or decreasing 33 ………… .
• the tree only grows near the 34 ………… .
• extracting the latex (rubber) is labour-intensive
• it is very difficult to 35 ………… rubber after production.
• New threats include
• lack of genetic diversity, leading to danger of disease caused by a 36 ………… .
• a shift to the cultivation of palm oil
• extreme 37 ………… events.
• Synthetic rubber
• may be used for engine parts and cooking utensils
• is less 38 ………… than natural rubber
• is unsuitable for many purposes e.g. the tyres of aircraft.
• An alternative source of natural rubber
• A wild flower (a type of dandelion) has rubber in its 39 ………… .
• It can be grown in many locations and does not require good 40 ………… .

Natural Rubber Lecture Listening Answers

Questions and Answers

Natural Rubber Lecture Answer Explanations

31. metal — the notes list the three resources essential for industrial civilisation, and the lecture opens with “One of these is metal”, followed by fossil fuels and then rubber. The key prints the singular, so write metal, not metals, and do not be drawn by machines or transportation, which the metal makes possible.

32. slow — the note stem is the growth of the tree is ……, and the evidence is “It can take eight to ten years for a tree to start producing rubber, so cultivating them’s a slow process”. The adjective slow completes the stem; writing the years themselves breaks the ONE WORD ONLY rule.

33. demand — the note explains why production cannot easily be adjusted, and ordinary farmers can react when they find “the demand for that crop is rising or falling”. Rubber growers cannot, because planting happens eight or ten years ahead. The noun the notes require is demand.

34. equator — the tree is choosy about temperature, rainfall and altitude, and the result is that it grows “only around the equator”. Temperature and rainfall are the traps, because they describe growing conditions rather than a position on the globe, and the stem needs a place.

35. recycle — water and glass are the contrast, since “when we’ve finished using them we can recycle them”, whereas with rubber the process is possible but very difficult. The stem reads it is very difficult to …… rubber, so a bare verb follows to and the answer is recycle.

36. fungus — the disease threat follows from “very little genetic diversity among the trees”, and the lecture states “The most dangerous threat is a fungus, which destroyed large numbers of rubber trees in Brazil”. Write the singular fungus, not fungi, to match the key.

37. weather — the notes end the threats list with extreme …… events, and the region has been “repeatedly hit by extreme types of weather”. Weather repeats the answer to Question 2 in Section 1, so keep the spelling identical across both parts of the paper.

38. strong — synthetic rubber suits engine parts and silicone cookware, but “compared with natural rubber, it’s not anything like as strong”. The notes use the pattern is less …… than natural rubber, so the adjective strong completes the comparison, and that weakness is why “only natural rubber can stand up to the extreme speeds of aircraft tyres”.

39. roots — the dandelion is a wild plant with yellow flowers, but the rubber is found when it is “pulled up and its roots cut open, they’re found to contain rubber”. Flowers is the trap, because the notes ask where the rubber sits, which is in its roots.

40. soil — the final note paraphrases the lecture: dandelions will “grow in all sorts of places, and they don’t need rich soil”. The notes swap rich for good, so soil is the last answer of the paper.

Listening Transcript — Section 4

Much of the world now lives in an industrial civilisation. But this has only become possible because we have the necessary natural resources. There are three types of natural resource without which industry could not exist. One of these is metal – without that we’d have no machines and no transportation. Another is fossil fuels, which we need to power those machines. But there’s a third resource that’s essential to connect the different parts of a machine together with belts and pipes and shock absorbers, and that is rubber. It’s now used in over 40,000 products, from waterproof footwear to surgical gloves.

At present, we have two types of rubber in common use. One is natural rubber, which nearly all comes from the Pará rubber tree. This was originally native to Brazil, but is now cultivated on plantations in South-East Asia. Recently, however, concern’s been growing that supplies may soon be insufficient for the world’s needs. So what exactly is limiting the supply of natural rubber?

Well, for one thing, rubber trees don’t just spring up overnight. It can take eight to ten years for a tree to start producing rubber, so cultivating them’s a slow process. And this leads to another problem. With most crops, farmers don’t have to think very far ahead, so they can easily change what crop they produce, or how much of a crop they produce, if they find the demand for that crop is rising or falling. But if you have to plant eight or ten years ahead, that’s much harder. And also the rubber tree’s very choosy about where it grows. It needs the right temperature, the right amount of rainfall, and the right altitude – not too high and not too low. The result is that it can’t be grown in the northern or southern parts of the globe, only around the equator. Another problem is that the rubber is basically extracted in the same way as it’s been done for hundreds of years, and that’s by hand, by making small cuts in the trunk of the tree, and putting a little cup there to catch the latex, as the rubber is called. It’s very labour-intensive. And it’s not just the initial production that’s limiting supplies. With other resources such as water and glass, when we’ve finished using them we can recycle them, but although this is also possible with rubber, it’s very difficult, so that also reduces the amount we have available.

And in the last few years, there have been new threats to the supply of natural rubber. One problem is linked to the fact that nearly all the rubber trees in South-East Asia are descended from just a small number of seeds brought from Brazil in the nineteenth century. This means that there’s very little genetic diversity among the trees, which in turn makes them very vulnerable to disease. The most dangerous threat is a fungus, which destroyed large numbers of rubber trees in Brazil, and which could cause devastation to plantations worldwide. Another problem is that farmers in South-East Asia are increasingly turning to the cultivation of palm oil, which is easier and more profitable for them. And finally, in recent years South-East Asia, like other parts of the world, has been repeatedly hit by extreme types of weather, and this looks likely to continue in the future.

However, as well as using natural rubber, it’s also possible to make rubber synthetically. This works very well for some purposes, for example, making engine parts, or silicone pots and pans used for cooking. But compared with natural rubber, it’s not anything like as strong, and this means it can’t replace natural rubber in other products. For example, while a mixture of natural rubber and synthetic rubber works well in car tyres, only natural rubber can stand up to the extreme speeds of aircraft tyres during take-off and landing.

So for some time, scientists have been looking for alternative sources of natural rubber. One that’s been known about for some time seems initially to be a rather unlikely source. It’s a wild plant with yellow flowers that we normally regard as a weed when we see it in our gardens. But when it’s pulled up and its roots cut open, they’re found to contain rubber.

Now, compared to the rubber tree, dandelions produce relatively small amounts of rubber, but unlike rubber trees, they’re very adaptable. They’ll grow in all sorts of places, and they don’t need rich soil. So at present there are several projects underway investigating the possibility of using dandelions as a source of rubber.

Another possibility is a desert shrub grown in Mexico and Texas …

Key Vocabulary and Spelling

Study Tips

Hold the ONE WORD ONLY limit for all ten questions, because three answers punish it directly. Question 32 needs the adjective slow, not the phrase eight to ten years; Question 36 needs the singular fungus, not fungi; Question 31 needs the singular metal, not metals. Write exactly what you hear, then check the word count of every answer against the limit before the recording ends.

The notes paraphrase the lecture, so match meaning rather than sound. The notes say many locations where the speaker says the plants will “grow in all sorts of places”, and good soil where he says “they don’t need rich soil”. Predicting the word class of each gap before the audio starts — noun after the, verb after to, adjective after is — keeps you ahead of the paraphrase, so build predicting answers before you hear them into your routine.

Track the five note headings as the lecture moves: sources of rubber, limits on supply, new threats, synthetic rubber and the alternative source. The speaker signposts each shift with phrases such as And finally and So for some time, and the ten gaps follow the headings in strict order. Spelling decides marks here too — equator, dandelions and labour-intensive all lose points when mistyped, so drill them with the listening spelling rules before test day.

Practice More Listening Tests

Add your Section 4 marks to the running total on the full Cambridge IELTS 21 Listening Test 1 answers page, which holds the keys, explanations and transcripts for all four sections of the paper. The free IELTS listening practice course from Simply IELTS strengthens the habits this lecture rewards: holding a strict word limit across ten unbroken questions and matching paraphrases at lecture pace. Test those habits on a parallel topic with this interactive listening test: maple syrup ielts listening test with answer, another paper drawn from trees and harvests, then revisit any section where the explanations show lost marks.