—How do you improve your listening, Mary?

—Just ______ listening to tapes, it's a good way, you know. [ ]

A. to

B. in

C. by

D. for

上颌侧切牙与上颌中切牙的区别中哪一点是错误的

A．上颌侧切牙唇面较窄小、圆突
B．上颌侧切牙舌窝窄而深
C．上颌侧切牙切缘向远中舌侧的倾斜度较中切牙大
D．上颌侧切牙近中切角似锐角
E．上颌侧切牙根长与冠长相近