Only when he read the newspaper _____ the US President Obama would deliver a speech in Fudan University.

A．he knew

B．he knows

C．does he know

D．did he know

软体动物中的斧足纲动物的闭壳肌长时间收缩依赖（）

A．平滑肌

B．横纹肌

C．斜纹肌

D．依种类而不同