Yusef is doing an experiment to find out how the amount of sunlight affects the growth of a seedling. he has three identical pots containing grass seeds that he planted at the same time. he puts them in windows that receive different amounts of sunlight each day. every day, yusef looks at the pots and records his observations. what is the variable in yusef's experiment? a. amount of water b. type of seedling c. type of soil d. amount of sunlight