Question

what component of earths atmosphere exists entirely as a result of photosynthesis?
oxygen gas
water vapor
nitrogen gas
carbon dioxide gas

Explanation:

Photosynthesis is the process by which plants use sunlight, carbon dioxide, and water to produce glucose and oxygen. Oxygen gas is a by - product of this process. Water vapor can come from evaporation of water bodies. Nitrogen gas has its own natural cycles and sources not related to photosynthesis. Carbon dioxide is taken in during photosynthesis, not produced as a result of it.

Answer:

oxygen gas