Question 13 of 25
 A scientist measures how quickly bamboo plants grow after receiving
 different amounts of water. She gives each plant a different amount of water
 and measures the plant's growth. What is the manipulated variable in this
 experiment?
 A. The total number of bamboo plants
 B. The number of days of the experiment
 C. The size of the bamboo plant
 D. The amount of water given