下井时（ ）必须携带便携式甲烷检测报警仪或便携式光学甲烷检测仪。
C
暂无解析
()Look!Thecatis_______.
属于知识密集型的高科技产业是()
Lookatthesign.Thelibraryis_____(close)from1:00p.mto2:00p.m.
Therearetwo_____inourschool
—Where_____you_____?
—I'mfromBeijing
