--- May we leave the classroom now?

--- No, you ____________ . You ____________ to leave before the bell rings.

A．mustn’t, are allowed

B．don’t have to, are allowed

C．needn’t, aren’t allowed

D．can’t, aren’t allowed

产后出血的主要临床表现为（）

A.子宫收缩乏力

B.胎盘原因

C.软产道裂伤

D. * * 流血过多

E.凝血功能障碍