The correct answer is D. The amount of food he feeds each mouse
Step-by-step explanation:
In research, the independent variable refers to the variable or factor that is manipulated by the researcher. Besides this, the independent variable affects the dependent variable or factor being studied. This implies in the case presented, the dependent variable is how shiny mice's fur is because this is the variable being studied; on the other hand, the independent variable is the amount of food Jorge feeds to each mouse because this is the factor Jorge would manipulate or change to prove if the amount of food has an effect on the fur of mice.