A good teacher always leaves his students enough time to think and voice their opinions in class，_________ sometimes he may not complete his teaching task．

A．even if        B．in case       C．as long as      D．as if

A good teacher always leaves his students enough time to think and voice their opinions in class, ______ he may not complete his teaching task.

　 A. in case 　　　　　 B. even if 　　　　　 C. as long as 　　　 D. as if