要分清这些词的用法,首先要知道他们有什么词性,可以出现在句子的那个部位.what可以做疑问代词,既有名词又有形容词的性质,when可以做状语,why表示原因可做名词,疑问代词,how可以做副词
这些词前面都可以加上that is ...或者It is.用于陈述句语句中.
例如That is how I feeled and what I feeled.
It was 10 o'clock when you came back yesterday.
还可以在前面加动词做宾语.
例如I dont' know what you like;
I'll tell you what;
He hurt me and I don't know why.
希望能帮到楼主!