《煤矿防治水规定》探水时，应从（）开始向前方打钻探水。
A、积水线
B、探水线
C、警戒线
D、掘进线
参考答案：B
液压元件组装方法及注意事项？
—You look unhappy. ?
—I have so much homework to do that I couldn't play soccer. [ ]
A. Do you feel sad
B. Are you ill
C. What's the'matter
