这两个词在句中的成分不同。
what to do sth在句中为宾语,也就是紧接在动词后,同理也有what to happen to me的结构,不过在句中充当宾语。例如:I want to know what to happen to me.
而what happened to me可以直接构成特殊疑问句,例如:what have happened to me ?
这是what两种不同的用法,一是后接不定式to构成宾语,二是用作特殊疑问词,引导特殊疑问句。
happen是不及物动词,
某人出了某事常用句型sth happen to sb
例如
A car accident happened to me yesterday.
提问a car accident 就是
what happened to me yesterday?
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