Here's a problem to solve: The types of organisms on Earth changed as a result of increased levels of atmospheric oxygen. Which process contributed to this buildup of oxygen in Earth's atmosphere?

Among the 4 following options, which is the correct answer?

- A: metabolic production of methane
 
- B: production of nitrates from inorganic nitrogen
 
- C: aerobic breakdown of sugars to release energy
 
- D: transformation of light energy into chemical bond energy
 