将下列句子改成单数形式。（注意冠词的使用）1. Are there any oranges on the table?
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2. These are old houses.
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3. Are these elephants or bees?
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4. Those are pictures of animals.
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1. Is there an orange on the table?
2. This is an old house.
3. Is this an elephant or a bee?
4. That is a picture of animal.