The only reason___he explained to me was that his mother was ill能不能填why或for which为什么?

问题描述:

The only reason___he explained to me was that his mother was ill
能不能填why或for which
为什么?

填 which
定语从句
先行词是reason
把先行词带入从句中应该是
he explained 【the reason】to me 充当宾语
用关系代词which

which
那个他唯一解释给我的原因是他妈妈生病了.
for的话语法上有错,这里要用定语从句,而且不通了,意为 为了\对于
why 不行,因为the only reason是它要指代的东西,是一个名词,只能用what\which,而根据意思判断为which,why的话要加一句句子(一个原因)

填that,在"the only+名词"之后只能用that