The passenger oxygen system is a chemically—generated oxygen system for use by passengers and cabin attendants."the chemically—generated oxygen"means "化学（方法）产生的氧气"
A.1
正确答案是A
The passenger oxygen system is a chemically—generated oxygen system for use by passengers and cabin attendants."the chemically—generated oxygen"means "化学（方法）产生的氧气"
A.1
正确答案是A