二、将简单句组成复合句

1.I was reading while she was writing.或While I was reading,she was writing.

1. In Mr. Wang's house I met several college students, all of whom were engaged in revolutionary work.

2. The English language is difficult, but it is less difficult than the Russian language because its grammar is much simpler.

3. Science is useful because it can benefit mankind,but it is also dangerous because it can bring harm to people if used by evil-doers.