I am only interested in doing nothing.That's ____ I'm interested in.

问题描述:

I am only interested in doing nothing.That's ____ I'm interested in.
A.only B.the one C.the only
Fishing is my favorite sport.It is ____.
A.the one i like best B.my best D.the best
能否解释下第一题为什么不选the one 的原因

为什么第一题选C?
不是应该选B吗?
这是一个缺少先行词的定语从句
That's the one which I'm interested in 定语从句 which在从句中做宾语,可以省略
或That's what I'm inerested in表语从句what 做in 的宾语