The right answer is D.
Tolerance occurs when a person consumes a substance for a prolonged period. The body becomes accustomed to its effects. This results in the need for higher and higher doses to feel the same pleasant effects as the first few times. Often, tolerance to pleasant effects sets in faster than tolerance to unpleasant effects. Concretely, it means that the person will be inclined to want to increase the doses, but by increasing them, He will feel more unpleasant effects!