The dog _____ for an hour. [ ]
A. died
B. has died
C. has been dead
D. would die
答案:C
突出煤层掘进工作面松动爆破时,必须有()、反向风门等措施。
A.撤人
B.警戒
C.停电
D.远距离爆破
冲裁大型和厚板零件时,为减少(),凸、凹模应采用斜刃口。
A.推件力
B.侧向力
C.冲裁力
D.卸料力