Which gas is utilized by plants during photosynthesis?

Plants utilize carbon dioxide during photosynthesis as a key reactant in the process of converting light energy into chemical energy. During this process, they absorb carbon dioxide from the atmosphere through small openings in their leaves called stomata.

The photosynthesis equation reflects this process: carbon dioxide combines with water in the presence of sunlight to produce glucose (a sugar used for energy) and oxygen as a byproduct. The glucose provides energy and serves as a building block for plant growth, while the oxygen is released back into the atmosphere, contributing to the air we breathe.

In contrast, other gases listed, such as oxygen, carbon monoxide, and methane, do not play a role in photosynthesis. Oxygen is a byproduct of the photosynthetic process rather than a reactant. Carbon monoxide is toxic to plants and does not participate in metabolic processes like photosynthesis. Methane, while a gas that is produced by some living organisms, is not utilized by plants in photosynthesis. Thus, carbon dioxide is essential for the synthesis of organic compounds in plants, making it the correct answer.