将下列各句改成一般疑问句并且给出简短的肯定和否定回答。
1. This is my pencil.
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2. His name is David.
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3. They are from England.
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4. Tom's father is a doctor.
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5. The desks are very heavy.
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6. Mary is doing her homework now.
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1. Is this your pencil? Yes, it is. No, it isn't.
2. Is his name David? Yes, it is. No, it isn't.
3. Are they from England? Yes, they are. No, they aren't.
4. Is Tom's father a doctor? Yes, he is. No, he isn't.
5. Are the desks very heavy? Yes, they are. No, they aren't.
6. Is Mary doing her homework now? Yes, she is. No, she isn't.