胸痹的主要病机是（）

A.气滞血瘀

B.气虚血瘀

C.肝阳上亢

D.气血不足

E.心脉痹阻

--- How _____ hours do you sleep a day?

--- Well, about eight hours. But how _____ sleep do we students really need?

A．many; many

B．much; much

C．much; many

D．many; much