I have lost the key_____the classroom,have you seen it?A of B to C for

问题描述:

I have lost the key_____the classroom,have you seen it?A of B to C for
这道题为什么选to,选其它两个答案行不行?

这是一个固定短语.the key to sth.有两个含义,一个是表示“……的钥匙”而另一个意思是“……的关键”其后必然搭配to.这里的to是介词.后面用名词,代词或动名词作宾语