大气中主要的污染物有（）、（）、（）、碳氢氧化物、硫化合物等。
参考答案：含氮化合物、碳氢化合物、卤素化合物
There are eight tips in Dr Roger's lecture on —sleep, and one of them is: _____ to bed early unless you think
it is necessary. [ ]
A. doesn't go
B. not to go
C. not going
D. don't go
农药残留
