Has oversight responsibility for the servicing and repair of her company's fleet of cars, so she 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

Variable-interval

Explanation:

she is likely to be reinforced with positive responses to her inquiries on a variable-interval schedule.

Variable-interval schedule is a schedule of reinforcement where a response is recompensed after an uncertain amount of time has passed, which is the opposite of a fixed-interval schedule.

answer; sales of books;

answerblank(1); fixed interval; blank(2) fixed ratio;