Answer:
A. extinction
Step-by-step explanation:
in this context,
CS : Conditioned Stimulus
CR : Conditioned Response
US : Unconditioned Stimulus
Extinction refers to a situation when a certain behavior started to dissapear when we don't reinforce that behavior for a certain period of time.
Here is an example:
Let's say that your mother always make a sound by Hitting frying pan to tell the rest of the house every time Dinner is ready.
So, you personally associate the sound from hitting the pan with delicious warm food. As a result, your mouth start to water every time you hear the sound of frying pan being hit.
In this case,
CS : sound of the frying pan ,
US : Unconditioned Stimulus
CR : You drooling because of the expectation of the food.
When you're 19, you move out of the house and live in the Dorm at college. In that place, your friends often hitting frying pan just to be used as acoustic drum rather than preparing food.
In this case,
CS is repeatedly presented in the absence of the US . (only the sound of frying pan without the food).
So overtime, you start to stop drooling every time you heard the sound of frying pan being hit. (the CR will "die out" )