The student had no choice but _____ his teacher ____ the mistake he had made.

A．to apologize to , for

B．to apologize, for

C．apologizing for, to

D．to apologize for, for

一束持续电子流在电场力作用下做匀加速直线运动，则在其周围空间[ ]

A．产生稳定的磁场   

B．产生变化的磁场

C．所产生的磁场又可产生电场    

D．产生的磁场和电场形成电磁波