you are supposed to do is it if you don’t like a thing. Don’t complain.A. That; changeB

问题补充：

you are supposed to do is it if you don’t like a thing. Don’t complain.

A. That; change

B. When; to change

C. What; change

D. What; changing

答案：

A. That; change

B. When; to change

(答案→)C. What; change

D. What; changing

解析：is前面的“ you are supposed to do”是主语部分，即主语从句，从句中的do后缺少宾语，用what引导，that在名词性从句中无意义，when作状语，排除A、B；当前面有动词原形do时，后面的不定式通常省略符号to，故选C。