In the Figure Below,why Is There a Seasonal Variation in Carbon

Multiple Choice

In the figure below,why is there a seasonal variation in carbon dioxide (CO₂) concentrations?

A) CO₂ concentrations rise and fall as photosynthesis decreases and increases.
B) CO₂ concentrations rise and fall in conjunction with power plant emissions.
C) CO₂ concentrations rise and fall with variations in solar radiation.
D) The measurements were made in different places at different times of year.