Answer:
The answer is 3. extinction.
Explanation:
In studies of conditioning, extinction refers to the gradual decrease in responsse to a stimulus. This may occur through habituation, as in the example; or after a prolonged period in which the stimulus has not been present (the person might discover he is no longer afraid of dogs after a long time without seeing or interacting with them).
A response that was believed to be extinct can suddenly reappear. This is called spontaneous recovery.
