Answer: Variable-ratio
Explanation:
Variable ratio schedule is defined as reinforcement schedule in which a response is reinforced after uncertain or sudden number of responses.It has the ability to generate high rate of response system with unpredictable factor. Example of variable ration schedule can be gambling game etc.
According to the question,Steve is reinforced into variable ratio schedule as chances of getting reward is uncertain because reward is given for assignment after number of assignment passes without any reward by instructor.
