Responses extinguish fastest when they are learned through which type of reinforcement schedule?

a. continuous

I believe the answer is: Continuous reinforcement schedule

In a Continuous reinforcement schedule, a reinforcement would be given to the subject only if the subject display some successful behaviors, not after each one.

By using this type of reinforcement schedule, we could keep the subject in a state where he/she would constantly seek rewards without knowing when to receive it.