Biology Practice Test 2026 – Complete Marking Period 3 Guide

Photosynthesis uses light energy to build a sugar from simple molecules. Plants take in carbon dioxide from the air and water from their tissues as the starting materials. Light energy powers the chemical steps that fix CO2 into glucose, with oxygen released as a byproduct from splitting water. So, the main reactants are carbon dioxide and water, and the main products are glucose and oxygen, with light energy driving the process. The other statements either misstate what’s consumed or produced, or omit the need for light energy.