下列哪一项决定牙移动的方式（）
A.力
B.力偶矩
C.力偶矩／力
D.力偶矩×力
E.力偶矩＋力
参考答案：C
Our teacher is very kind to us. So we regard her ________our best friend.
A．on
B．to
C．as
D．at
