问题详情

27 Air pollution can be as harmful to one"s health___________
28 Traveling on an underground train can reduce exposure___________
29 Pollution levels are lower__________
30 It"s wise to stay away from heavy traffic____________
A on the downwind side
B during rush hours
C in spring and autumn
D to toxic air
E between autumn and winter
F as exposure to nuclear radiation请帮忙给出正确答案和分析，谢谢！