Final answer:
For the Cartesian Diver Experiment, the correct answer is C: Volume decreased, pressure increased, following Boyle's Law which dictates an inverse relationship between pressure and volume.
Step-by-step explanation:
In the Cartesian Diver Experiment, the diver submerges when pressure is applied to the bottle because of Boyle's Law, which states that pressure and volume of a gas are inversely related. When pressure increases, the volume decreases, and vice versa. Therefore, if the diver goes down when pressure is applied, the correct answer is that the volume of air in the diver decreases, and consequently, the pressure inside the diver increases, matching option C: Volume decreased, pressure increased.