NO₂ Concentrations During Photochemical Smog Events Often Have Two Peaks

NO₂ concentrations during photochemical smog events often have two peaks, one in the early morning (8 A.M.) and another, smaller peak around 7 P.M. The second peak is due to ________

A) NO₂ emissions produced during the evening rush hour.
B) the reaction of NO and O₃.
C) the photochemical formation of O₃.
D) automobile NO emissions reacting with oxygen.
E) all of the above.