Deer are eating Mr. Thompson's rose bushes. He puts a new deer repellent point on half of his rose bushes and then waters them. He uses the same amount of water on the other half of his rose bushes but does not put the repellent on them. What is the control group for his experiment? A: the rose bushes with deer repellent
B: the rose bushes without the deer repellent
C: the amount of water used
D: the type of brush used