This is the key __the door.A of B with C to D in

问题描述:

This is the key __the door.
A of B with C to D in

答案是C
有一些名词符合这种用法,有的具有两者息息相关,缺一不可的含义.如:key to door,invitation to party,
guide to action,limitation to life,accessory to school

c
一把钥匙开一把锁

TO,是英文的固定搭配,又如THE ANSWER TO THE QUESTION一样的

to 选 C