Students in ms. fullhart’s class were designing an experiment to test whether the amount of water given to a plant affects the growth in terms of height of the plant. both plants were given the same amount of plant food, and exposure to sunlight. the students decided to use potato plants to conduct their tests. the plants were all the same height when they started the test. the plants were divided into 4 groups of 3 plants each. group 1 plants were given no water, group 2 plants were given 10 ml of water each day, group 3 plants were given 50 ml of water each day, and group 4 plants were given 100 ml of water each day. what are the controls variables (constants)?