People in Zhejiang are proud of ______ they have achieved in the past few years.   [ ]

A. that

B. which    

C. what

D. how 

我国经济体制改革的中心环节是( )。

A．国有企业改革

B．培育市场体系

C．加强宏观调控体系

D．健全社会保障制度