Question

what do plants require as reactants for photosynthesis?
carbon dioxide and water
oxygen and water
carbon dioxide and sugar
oxygen and sugar

Explanation:

Photosynthesis in plants uses carbon dioxide ($\ce{CO_2}$) and water ($\ce{H_2O}$) as reactants, along with light energy, to produce glucose and oxygen. The other options include products (oxygen, sugar) or incorrect combinations.

Answer:

A. carbon dioxide and water