It is none of my business. It's up to you to decide he bought yesterday is used for.
A. what what
B. what that
C. that what
D. that which
网友回答
(答案→)A. what what
B. what that
C. that what
D. that which
解析：本题考查名词性从句。decide后接宾语从句；在宾语从句中he bought yesterday又是个主语从句，缺主语故用what。在宾语从句what he bought yesterday is usedfor中for缺宾语，故还要用what。