Final answer:
In Connor's experiment on rats, the independent variable is the diet of the rat, and the dependent variable is the rat's overall health.
Step-by-step explanation:
The experiment that Connor wants to conduct to determine if the diet of a rat has an effect on the rat's overall health involves two main types of variables: the independent variable and the dependent variable. In this scenario, the diet of the rat is the independent variable because it is what is being manipulated or changed in the experiment. The rat's overall health is the dependent variable because it is expected to change in response to changes in the rat's diet; thus, the health of the rat depends on the diet provided. Therefore, the correct answer is 'b. Independent: Diet; Dependent: Rat's overall health.'