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