牙轮钻头的牙齿磨损分级共分()个级。
A、2
B、3
C、4
D、5
参考答案:C
The programme, which refers _____ the tomb of Qin Shihuang, is _____ for those who are interested in history.
A.as; meant
B.for; intended
C.to; planned
D.to; intended
简述制定进入管制政策的基本思路。