Because she is responsible for overseeing the servicing and repair of her company's fleet of cars, rhonda frequently calls the garage mechanic to inquire whether service on various cars has been completed. because service completion times are unpredictable, she is likely to be reinforced with positive responses to her inquiries on a schedule.

she is likely to be reinforced with positive responses to her inquiries on a VARIABLE INTERVAL SCHEDULE.

Explanation:

Variable interval schedule refers to a reinforcement in which a response may be received after an unknown period of time has passed.

Schedule refers to how many times the reinforcement is applied.

Variable refers to the fact that time varies from one test to another.

Interval refers to the fact that response is controlled by time .