a plant requires sunlight for photosynthesis & if something is required for a process then that something is used for that process ->  a plant uses sunlight to perform photosynthesis  a plant uses sunlight to perform photosynthesis & photosynthesis makes food for the plant by converting carbon dioxide, water, and sunlight into carbohydrates ->  a plant uses sunlight to make food for itself  a plant uses sunlight to make food for itself & a tree is a kind of plant -> a tree uses sunlight to make food for itself