It is the interaction between people, rather than the events __ occur in their lives, __ is the main focus of social psychology.

A．that, that

B．that, which

C．which, which

D．that, what

引起鸡小脑软化的病因是（）。

A.链球菌

B.猪瘟病毒

C.食盐中毒

D.缺乏

E.硒缺乏