Mary _______ her mother with the housework, but she didn’t.  

A．must have helped

B．ought to have helped

C．must help

D．should help

不是评价项目活动质量主要采用的调查方法是（）。

A.定性调查

B.问卷调查

C.观察法

D.深入访谈

E.专题讨论