The origin of the gases called oxides of nitrogen in the atmosphere begins ____.
a. in the stratosphere
b. in the troposphere
c. in the mesosphere
d. with precipitation
e. with ice
Question 2
Ozone, PAN, and small amounts of other oxidating pollutants are the ingredients of photochemical smog and grouped under a single heading called ____.
a. NOx compounds
b. volatile organic compounds
c. hydrocarbons
d. radicals
e. photochemical oxidants