The boy has a handsome face _____ the scar on his forehead. [ ]

A. except

B. except for

C. except that

D. besides

同类或可以互相代替的货物的相向运输被称为( )运输，它是不合理运输中最突出、最普遍的一种。

A．对流
B．重复
C．无效
D．迂回