连词成句。
1. on, a, the, there, picture, nice, is, wall (.)
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2. are, workers, there, in, many, factory, the (?)
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3. cows, are, many, there, over, there (.)
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4. in, three, there, people, are, family, my (.)
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5. is, an, there, sofa, the, umbrella, near (.)
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，若
变为原来的4倍，为要保持相互作用力大小不变，则r变为原来的2倍。