Answer:
a. dishabituation
Step-by-step explanation:
In psychology, the term dishabituation refers to when a person shows a new interest in a new stimulus that occurs when a change in the stimulation is really intense so the person pays attention to the environment again. In other words, the person first became habituated to the stimulus because it was shown to him/her too many times but then a sudden change makes the person show interest again.
In this example, a baby has given 100 presentations of a high-pitched tone and he is no longer responding to it (he became habituated to the stimulus and lost interest on it). However, a low-pitched tone is presented (which is totally different from the high-pitched one) and the behavior of stopping sucking is back. Therefore, this is an example of dishabituation.