Answer:
Option C==> extinction.
Step-by-step explanation:
In Psychology, there is an aspect which is about or related to learning things and this concept is known as classical conditioning. So, in classical conditioning EXTINCTION is an element of the the concept. So, before I give the definition of extinction let me make an example in the next paragraph which is somewhat close to the experiment conducted by Ivan Pavlov(Russian Psychologist).
Imagine you conditioned or train your pet that whenever you ring a bell then it is time for food. So, whenever you ring that bell your pet runs to you in joy and salivates and because your pet knows that it is time for it to eat. Then, after sometimes whenever you ring the bell the pet does not see you will any food and do this for sometimes. After some days your pet will not run to to again because to the pet the ringing of the bell does not hold any meaning. This is what is called EXTINCTION.
Extinction is defined as what happens in classical conditioning when a conditioned stimulus is present but there is no more conditioned response.