儿童乳磨牙龋坏，根管治疗后的处理是（）
A.充填治疗
B.金属嵌体
C.塑料全冠
D.金属全冠
参考答案：A
----- It was a red light, William. You ________ the car.
------- Sorry, I didn’t see it.
A．must stop
B．should stop
C．must have stopped
D．should have stopped
LAN的数据链路层又可分为（）子层和（）子层。
