Extinction occurs as behavior due to lack of reinforcement.
a. immediately stops
b. tends to fluctuate
c. gradually strengthens
d. gradually diminishes

The right option is; d. gradually diminishes

Extinction occurs as behavior gradually diminishes due to lack of reinforcement.  

Extinction is the gradual weakening of a previously learned behavior, due to lack of reinforcement which causes the behavior to decrease or disappear (eventually stops). Extinction can happen in all types of behavioral conditioning, but it is usually associated with operant conditioning (learning process through punishments and rewards for behavior).

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a photo collage of women at work during world war 2