What are you looking for?I'm looking for the pen____I bought yesterday.

问题描述:

What are you looking for?I'm looking for the pen____I bought yesterday.
A.which B.that C./ D.A,B&C

D
A,B,C 都对,故选D
先行词是物,关系代词在定语从句中作宾语,可以是which,that,或者省略