photosynthesis is a kind of process & if something is used by a process to make something else, then that something is required to perform that process ->  if something is used by photosynthesis to make something else, then that something is required to perfrom photosynthesis  if something is used by photosynthesis to make something else, then that something is required to perfrom photosynthesis & photosynthesis is a source of / makes food / energy for the plant by converting carbon dioxide, water, and sunlight into carbohydrates ->  a plant requires sunlight for photosynthesis  a leaf is a part of a green plant & leaves contain chlorophyll ->  a leaf is a part of a green plant that contains chlorophyll  a leaf is a part of a green plant that contains chlorophyll & chlorophyll is a part of a plant used to perform photosynthesis ->  a leaf is a part of a green plant that is able to perform photosynthesis  a leaf is a part of a green plant that is able to perform photosynthesis & green plants provide food for themselves / animals / consumers by performing photosynthesis ->  a leaf performs photosynthesis  a plant requires sunlight for photosynthesis & a leaf performs photosynthesis -> a leaf requires sunlight to perform photosynthesis