使用RH一31T测爆仪测量某地区的可燃气体含量，若仪器指针指示到1

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问题单项选择题

使用RH一31T测爆仪测量某地区的可燃气体含量，若仪器指针指示到100％时，表不此时该地区空气中天然气的浓度已达到了()

A、100％;

B、50％;

C、15％;

D、5％

答案

参考答案：D

选择题

I regret _____ hard at school, or I would have succeeded in passing the exam.

A．not to work

B．having not worked

C．to have not worked

D．not having worked

选择题

______ is no doubt that the Rockets will defeat the Washington Wizards in the next

game.

A．It

B．As

C．That

D．There