单项选择题A.He travels all over America to help put out fires. B.He often teaches children what to do during a fire. C.He teaches Spanish in a San Francisco community. D.He provides oxygen masks to children free of charge.
单项选择题A. It may make the wearer feel tired. B. It will gradually weaken the eyes of adults. C. It can lead to the loss of vision in children. D. It can permanently change the eye structure.