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 a process by which plants, algae, and some bacteria use sunlight, carbon - dioxide, and water to produce glucose and oxygen. Oxygen gas in the Earth's atmosphere is mainly a by - product of photosynthesis. Water vapor comes from evaporation and transpiration, nitrogen gas has various natural and industrial sources, and carbon dioxide gas is released through respiration, decomposition, and burning of fossil fuels.

Answer:

A. oxygen gas