Ascientist is testing the effectiveness of drug x on cancer. she gives a small amount of the drug to mice that have cancer. she gives each mouse a different amount from 1 to 10 grams, and then measures the size of the tumor in each mouse before the drugs and two weeks after the drugs. she gives one of the mice sugar instead of drug x. what is her control this experiment? a: the ammount of drug x given to the mice. b: the size of the of tumor before drugs x. c: the size of the tumor after drug x. d: the mouse that received sugar instead of the drug x