1.汤姆正在车站等车时看见一位老朋友。
When I was waiting
2.我做作业时灯灭了。
While I was doing my homework,the light went out(不能用turn out,因为的它自己灭的,不是人关的)
3.学生们正在说话时老师进来了。
While the students were talking, the teacher came in.
when tom is waiting
while i was doing my homework, the light turn out.
while the students were talking,the teacher coming in