Atmospheric carbon dioxide levels have been increasing from year to year. However, in locations in the
northern hemisphere, carbon dioxide levels may decrease slightly during the summer months. Which is
the MOST likely explanation for these slight summertime decreases?
(A) an increase in the rate of cellular respiration during the summer
(B) a decrease in the rate of cellular respiration during the summer
(C) an increase in the rate of photosynthesis during the summer
(D) an increase in the rate of nitrogen fixation during the summer
(E) an increase in the frequency of thunderstorms and hurricanes during the summer