A. should be worn while fighting a fire B. can be used in atmospheres deficient in oxygen C. filter contaminants from air that is to be breathed D. may be substituted for a self-contained breathing apparatu
A. 稳定物价 B. 充分就业 C. 保持货币币值稳定 D. 促进经济增长
A. 低温 B. 低湿 C. 低氧 D. 以上均是
A. 正确 B. 错误