Before __ the trunk must be checked. A．u

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问题选择题

Before __ the trunk must be checked.

A．used

B．to use

C．being used

D．to be used

答案

答案：C

选择题

There _____an old tree here. I wonder how they could manage to remove such an old tree.

A．seemed not

B．not seemed

C．didn’t seem to be

D．didn’t seem to have

填空题

如果把打气筒的出气口封住，在活塞下压的过程中，被密闭的气体的质量 _________ ，体积 _________ ，密度 _________ ．（填变大、变小或不变）