Question 409
HardOriginal questionFor more than two hundred years, since the , people have been burning coal, oil and gas and changing the way land is used. As a result, the amount of carbon dioxide in the air has been rising.
The ocean takes in about thirty per cent of the carbon dioxide released into the air. That might sound like a good thing, and in one way it is, since it keeps some of the gas out of the atmosphere. But it changes the sea. When carbon dioxide dissolves in sea water, a chain of chemical reactions makes the water more . This slow change is called ocean acidification.
The change matters most to creatures that build shells and . Oysters, clams, sea urchins and corals all use substances called carbonate ions as building blocks. In more acidic water there are relatively fewer of these, so building and keeping a shell becomes harder.
Even animals without shells can be affected. In more acidic water, some fish become worse at sensing the that hunt them. And when the creatures at the bottom of a are in trouble, everything that eats them may be in trouble too.
Why is acidification especially hard on oysters, clams and corals?
Show the answer and explanation
Correct answer: A
Explanation
The third paragraph says these creatures use carbonate ions as building blocks, and in more acidic water "there are relatively fewer of these".
Worth noting
The passage does not mention swimming or cold water; the reason is the building blocks.
- Concept
- Following a cause-and-effect explanation
- Typical timeTypical
- 55 s
- Your timeYours
- —
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