C. A higher amount of addictive chemicals are needed to get the same high when fewer receptors are present...
Answer:
The nervous system is stimulated from the environment, through sensory receptors. A stimulus is any form of energy that can be detected by the body. ... Animals normally only respond to stimuli which they select; they filter out certain stimuli that surround them, and react to others they choose to accept.
I'm going with C. It may be wrong but I think it's C.