Answer:
variable-interval
Explanation:
Variable-interval schedule: In psychology, the term variable-interval schedule is considered as a reinforcement schedule that is being used widely in operant conditioning.
In the variable-interval schedule of reinforcement, reinforcement is being given to subject's or participant's response after the particular period has elapsed i.e, unpredictable time, and the time is supposed to be on changing or variable schedule.
In the question above, the statement signifies the variable-interval schedule of reinforcement.
