________ all the homework assigned by the school, the students have to work at it till midnight.

A．Completing

B．To complete

C．Having completed

D．To have completed

在下列关于华法林的描述中，错误的是（）

A.口服吸收完全

B.体内、外均有效

C.体外无效

D.抗凝血作用出现慢

E.维持时间久