使用安全卡瓦时，卡平卡正管体，要求（）卡瓦牙都咬紧管体。
A.2/3
B.全部
C.1/3
D.4/5
参考答案：B
Jeff goes to work _____and his wife goes to work [ ]
A. by car;on her bike
B. by a car; her bike
C. by cars; by bike
D. by his car; by bike
下面对牙冠邻面的解释错误的是
A．前牙接触区的切龈径大于唇舌径B．前牙接触区靠近颈缘部位C．良好接触区可分散骀力D．随年龄增长接触点变为接触面E．后牙接触区靠近耠缘部位
