题目内容：

I happened _____ with him when a ball hit him on the head.a.to be talking b.to have talked c.
选A
c.to talking d.to talk

优质解答

选a
当一个球砸到他的头部时我恰巧正在和他谈话
1.when在这里是表示过去进行时,happened to是碰巧 be在这里不是表被动,而是谓语动词,你可以试着先去掉happened to这个副词试试,去掉后就变成了I be talking with him when a ball hit him on the head.句子依然成立
2.happened to do sth,我们习惯这个词组,但是这个题主要是when是个连词,之前用进行时