Question 406
MediumOriginal 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.
What is the passage mainly about?
Show the answer and explanation
Correct answer: D
Explanation
The passage explains how the ocean takes in carbon dioxide, how that makes it more acidic, and how the change harms shell-builders and other creatures.
Worth noting
Oysters are one example of the creatures affected, not the subject.
- Concept
- Finding the central idea of a passage
- Typical timeTypical
- 45 s
- Your timeYours
- —
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