B is the correct answer. The independent variable is the factor that is controlled by the experimenter, in this case, the amount of fat consumed. The dependent variable is the measured value that changes in response to the independent variable, in this case, change in weight. The experiment in choice D would measure the effect on weight of dietary calories, not the effect fat has in the diet.
B is the correct answer. The independent variable is the factor that is controlled by the experimenter, in this case, the amount of fat consumed. The dependent variable is the measured value that changes in response to the independent variable, in this case, change in weight. The experiment in choice D would measure the effect on weight of dietary calories, not the effect fat has in the diet.