煤层气的防爆措施主要有（）。
A.工艺防爆
B.建筑防爆
C.电气防爆
D.环境防爆
参考答案：A, B, C, D
—The weather is very good. Let's go to the seaside.
— _________. Why not?[ ]
A Have fun
B. Not really
C. Sounds fine
D. Not at all
高效过滤器滤除（）粒径的颗粒。
A.粒径≥5.0µm
B.粒径≥1.0µm
C.粒径≥0.3µm
D.粒径≥0.1µm
t all