The process of photosynthesis arose roughly two billion years ago. Its origin had a huge impact on existing organisms and on the physical characteristics of the biosphere. Which major physical change could be attributed to photosynthesis?
A) Photosynthesis allowed much higher levels of ultraviolet light to reach Earth's surface.
B) Photosynthesis drastically raised Earth's surface temperature.
C) Photosynthesis drastically increased the oxygen content of the atmosphere.
D) Photosynthesis drastically increased the carbon dioxide content of the atmosphere.
Answer: C