完成句子。

1. — Are you still thinking about yesterday's game?

    — Oh, that's _____ (让我激动的事).

2. I wonder _____ (我们能做点什么) about it.

3. _____ (他不能明白的是) was why fewer and fewer students showed interest in his lessons.

4. Mary wrote an article on _____ (为什么这个队没赢得比赛).

5. The problem is _____ (谁要来帮助我们).

真空可以促使化学反应向生成（）的方向移动。