— You should have come to the party last Saturday evening. It was really fantastic.

— But a friend          an unexpected visit to me.  

A．paid

B．had paid

C．would pay

D．has paid

双代号时标网络计划的编制方法主要有( )。

A．直接法

B．间接法

C．母线法

D．指向法

E．过桥法