Apart from being pollutants on their own, __1___ have at least two major effects on the atmosphere. First, when they react with water vapor and oxygen, they produce nitric acid, causing acid rain. Further, their reactions produce__2____in the lower atmosphere.

Blank 1
A. oxides of carbon
B. nitrogen oxides
C. methane and ethane

Blank 2
A. ozone
B. sulfur dioxide
C. carbon monoxide