按要求完成下列句子。
1. We are making a model plane. (改为一般疑问句)
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2. The boys are sitting under the tree. (对画线部分提问)
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3. Look out of the window. (改为否定句)
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4. We can see some birds over there. (对画线部分提问)
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5. The children have some apples. (改为单数句)
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