Professor James will give us a lecture on the Western culture, but when and where            yet.      [ ]

A. hasn't been decided          

B. haven't decided      

C. isn't being decided          

D. aren't decided

在现实生活中，价值规律对市场中商品生产和交换活动的支配作用主要是通过（）表现出来的。

A．价格运动

B．交易规模

C．交易范围

D．交易方式