Have you asked her for the reason____may explain her absence
4个回答

先把这个句子换成陈述句来讲,你就好理解了:

You have asked her for the reason____may explain her absence

主语You 谓语have asked 间接宾语her 直接宾语 reason

简单来说,reason是名词,____may explain her absence做reason的定语从句,翻译过来就是:可以解释他缺席的那个(that)原因

如果填what,就翻译成 可以解释他缺席的什么(what)原因,说不通

词性上来说,reason是名词,what也是名词,两个非组合名词不能连在一起,而that 可以做代词,取代reason在定语从句中做主语,that may explain her absence