翻译下列句子。
1. You should be quiet when you are in the reading room.
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2. When I grow up, I'll be a nurse and look after patients.
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3. If you don't want to go alone, I'll go with you.
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4. After you use plastic bags, you mustn't throw them about.
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5. People in the USA can't drink beer or wine before they reach 21.
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