【题目】—We've only got this small bookcase. Will that do?
—No,I am looking for is something much bigger and stronger.
A.who
B.that
C.what
D.which

【答案】C
【解析】句意：——我们仅有这个小书箱。那个合适吗？——我正在找的是比这更大、更结实的书柜。此处what I am looking for是主语从句，what在主语从句中作for的宾语。故答案选C。