Answer:
b. sensory adaptation.
Explanation:
In psychology, the term sensory adaptation refers to the phenomenon that occurs when our sensory receptors are constantly exposed to some stimuli (like loud noises) and so they get adjust to them and stop perceiving them as part of the environment and therefore, they become less noticeable.
In this example, There is a short in the light in one office and it makes a soft but constant sound. When Travis walks into the office he asks about that awful noise but Holden (who works there) doesn't hear it anymore. We can see that Holden has been constantly exposed to this soft constant high-pitched sound so he got adjusted to it and stopped perceiving it. Therefore, he has experienced sensory adaptation.