按要求改写句子。
1. These are my friends.(改为单数句)
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2. This is my little sister.(改为一般疑问句,并作肯定回答)
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3. She is a clever pupil.(改为否定句)
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4. Are you fat?(作否定回答)
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5. It is a very naughty bird.(改为一般疑问句,并作否定回答)
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