按要求变换句型。

1. Su Yang is cleaning the library now. (将now换成often)

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2. We did some shopping yesterday. (变成一般疑问句)

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3. The new comb is hers. (对画线部分提问)

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4. There was some milk in the bottle. (变成否定句)

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5. they, on, last, did, the, the, milk, farm, Saturday, cows (连词成句)

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逆流式机械通风冷却塔的进风口面积和淋水面积之比不小于（）。