The main purpose of photosynthesis is to a. produce the food the plant needs to grow. b. convert carbon dioxide gas to oxygen gas. c. absorb sunlight to stop the plant from overheating. d. allow the plant to dispose of excess water.

Convert carbon dioxide gas to oxygen gas.

produce the food the plant needs to grow.
However, some folks have missed the purpose of photosynthesis. It's not oxygen production. The primary function of photosynthesis is to convert solar energy into chemical energy and then store that chemical energy for future use. For the most part, the planet's living systems are powered by this process