硬质合金刀具最常用的砂轮是（）砂轮。
A．黑色碳化硅
B．绿色碳化硅
C．白刚玉
D．铬刚玉
参考答案：B
It’s said that _____ people flew to Paris during the Easter weekend.
A. thousand of B. two thousand C. two thousand of
构形后缀
