球团矿筛分指数级别范围：一级品＜（）%，二级品＜（）%。
参考答案：5；5
---David has made great progress recently.
--- _____, and _____.
A．So he has; so you have
B．So he has; so have you
C．So has he; so have you
D．So has he;so you have
在有煤与瓦斯突出危险的矿井中进行焊接作业时，必须（）。
A.停止突出危险区的一切工作
B.切断突出危险安全源
C.撤出突出危险区人员
