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1. It is necessary                (sit) down to have a rest.

2. If he____(be)to come, what should we say to him?

3. These water cups         ____(make) of paper.

4. Their medical team(医疗队)         ____(make) up of doctors ,nurses and other skilled members.

5. There would no longer   ____(be) lives if there       ( be) no water on earth.

大气压随海拔高度的升高而减小，1654年德国的马德堡市的市长做了历史上有名的______实验验证了大气压强的存在，17世纪40年代意大利科学家______用实验首先测出了大气压的值．