—I can never forget the days       we spent together in the summer camp.

—Well, especially the day       it suddenly began to rain in the middle of the night.

A．when; when

B．which; when

C．what; that

D．on which; when

房地产市场的运行环境包括很多方面，其中有( )。

A．社会环境

B．自然环境

C．房地产法律制度环境

D．国际环境

E．政治环境