Eremy goes to crowded parties and approaches women with a cheesy pick-up line designed to get their phone numbers. Jeremy never knows which women will fall for his line, but he does know that if he asks enough women, it's quite probable that he will get a phone number. Jeremy's behavior is being reinforced on a schedule.

variable-ratio      

Explanation:

Variable-ratio schedule: In psychology, the term "variable-ratio schedule" is described as one of the different reinforcement schedules of the operant conditioning theory which was proposed by B. F. Skinner.

It is described as a reinforcement schedule in which a specific response is being "reinforced" after every unpredictable or unforeseeable number of responses. Variable-ratio schedule ought to create a high and steady responding rate.

In the question above, the given statement states that Jeremy's behavior is being reinforced on a variable-ratio schedule.

d. the polar jet stream   lies between the polar easterlies and trade winds should be your answer