Our special thanks to go thousands of volunteers, without ____tireless work, none of this would be possible.

A．which

B．whom

C．whose

D．that

（）标志着产业组织理论体系的初步成熟，产业经济学因此成为一门相对独立的经济学科。

A.有效竞争理论

B.马歇尔冲突

C.SCP范式

D.垄断竞争