清肝引经汤治疗经行吐衄的适应证候是（）

A.肺肾阴虚证

B.湿热瘀结证

C.肝经湿热证

D.肝经郁火证

E.气滞血瘀证

How（）you say that you really understand the whole story if you have covered only part of the article?

A.can  

B.must 

C.need  

D.may