随机应变:根据括号中所给的单词,填入正确的单词形式。将答案写在答题卷的相应位置上。
He left the room without ________________ (say) a word.
He volunteers ____________ (offer) to clean up the city park.
The higher the ground is, the______________(thin) the air will become
I want him to know the idea of ________ (fair).
I was__________(sweep) the floor at 8:00 yesterday morning.