Final answer:
B. A variable interval schedule is a schedule of reinforcement in which the first response after a varying period of time is reinforced. It is unpredictable and occurs based on changing amounts of time between responses.
Step-by-step explanation:
A schedule of reinforcement in which the first response after a varying period of time is reinforced is called a B. variable interval schedule.
This means that the reinforcement occurs based on unpredictable and changing amounts of time between responses.
An example of this would be a restaurant manager who rewards their staff with a bonus every once in a while when the quality control person comes to check the restaurant.