题目内容：

请阅读下面短文，按要求完成后面的小题，并将答案写在答题卡相应的位置上。

What is the most stressful thing in school? It is probably exams.Exams can put us under a lot of pressure.But some students do well under pressure，while others feel terrible.So，why do some students perform better under stress?

It all comes down to dopamine(多巴胺)．Dopamine is a chemical(化学物质) in our brain that sends signals(信号) to our body.It has many important roles：influencing memory，attention and how we learn.Our brains work best when there is a balance of dopamine — not too much or too little.

大脑通过两种方式控制多巴胺。It either takes out dopamine quickly，or gradually.Exam success can be connected to how fast dopamine goes back to a balance.

What happens when we take an exam? If you become stressed，your brain will start to overload(超负荷) on dopamine.It is like a cup overflowing with water.The quicker you can go back to a balance of dopamine，the quicker you will concentrate，helping you perform better on a test.

Scientists found that，during a test，people who slowly got back to a balance of dopamine scored 8 percent lower.That's the difference between a good mark and a bad mark.

But don't fear，there is some good news.The__study__also__found__that__the__more__practice__you__get，the__less__stressed__you'll__be.So，it turns out that practice really does make perfect.

1.What roles does dopamine play?

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2.请将文中的汉语翻译成英语。

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3.The writer talks about a cup overflowing with water to explain ________.

A. how to deal with stress

B. how to hold the cup with water

C. how the brain balances dopamine

4.请将文中画线部分翻译成汉语。

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5.The topic of the passage is about ________ and ________.