中等稳定顶板工作面初撑力不小于()KN。
A、50
B、80
C、90
D、70
参考答案:D
(二)
情况五中的试运行方案应由谁编制由谁审批
A.It can only alert the police.
B.It is of no use.
C.It can prevent the car being broken into.
D.It is really too expensive.