引气系统为飞机提供高压气源用于

If it    （）      rain, we （）        get wet.

It is required that you    （）        at six.

If he had not gone out in the storm （）          .

The boy acted     （）       he had never lived in Canada before.

He demanded that the laboratory report （）    immediately after the experiment was done.

He is not （）        a fool   （）     .

A steel plant is a place      （）   I am longing to visit these years.

Do you know who lives in the building   （）       there is a well.

She had three sons, all   （）       became doctors.

I, （） your good friend, will try my best to help you out.