The boy         the first prize, but he was so careless as to make a foolish mistake.

A．must have gained

B．need have gained

C．could have gained

D．shall have gained

将直通车流编入摘挂列车，属于违反（）的规定。

A、列车编组计划

B、《技规》

C、《行规》

D、列车运行图