The boy was doing homework while his mother      dinner.

A．cooks

B．cooked

C．was cooking

D．will cook

下列哪项是无排卵型功血的临床表现：（）

A.长时间出血不能自止

B.月经量多，周期正常

C.周期缩短，经量正常

D.基础体温后半期上升幅度偏低

E.多发生于生育年龄的妇女