Keesha did an experiment to study the rate of photosynthesis in the water plant elodea. she placed a piece of elodea in a beaker of water and set the beaker 10 centimeters (cm) from a light source. keesha counted the bubbles released from the plant every minute for five minutes (min). she repeated the process two more times. first, she moved the light to 20 cm from the beaker, and then she moved the light to 30 cm from the beaker. what is the outcome variable (dependent variable) in this experiment? what is the key phrase that tells you what you are looking for?