9. a biologist wants to know how the absence of a certain mineral nutrient will affect the bone growth of a laboratory rat.
the biologist performs the following four experiments. experiment 1: feeds the rat 100 mg of the nutrient a day, and
measures bone growth over 30 days. experiment 2: feeds the rat 50 mg of the nutrient a day, and measures bone
growth over 30 days. experiment 3: feeds the rat 25 mg of the nutrient a day, and measures bone growth over 30 days.
experiment 4: feeds the rat 0 mg of the nutrient a day, and measures bone growth over 30 days. which is the control
experiment?
o a. experiment 1
o b. experiment 2
o c. experiment 3
o d. experiment 4