In " How much do you think he earns？" how much is ______ of the sentence. （2009年考试真题）

In " How much do you think he earns？" how much is ______ of the sentence. （2009年考试真题）

A．the subject

B．the adverbial

C．the object

D．the complement

请帮忙给出正确答案和分析，谢谢！