To investigate seed growth in different levels of light, Jarrod covers seeds with soil in three different containers. He places a pea seed in a short, wide plastic cup, a cucumber seed in tall, skinny glass, and a tomato seed in a shallow, plastic dish. He places the plastic cup in a window sill in direct sunlight, the glass outside in partially shaded area, and the dish in his closet in the dark. He will leave the containers in those places for one week, and record the growth at the end of his investigation. How could Jarrod's investigation be adapted to create a fair test