参考答案：D

解析：[听力原文]22-25M: Hey Linda, do you get that letter about the new options for food service next year W: Not yet. Are there a lot of changes M: There sure are. Instead of paying one fee to cover all meals for the whole school year, we are now able to choose by seven, ten, fourteen or twenty-one meals per week. They give you a card with the number of meals you get for a week marked on it.W: That’s a big change, Tom. And a complicated system.M: Yeah. But it will be much better for people who don’t eat three meals a day, seven days a week in the cafeteria because they don’t have to pay meals they don’t eat.W: So what’s the deal for those who do eat at school all the time M: It’s better for them too. Because the meal you contract, the cheaper each one is.W: I see. It is still sound rather complicated.M: True. It took me several hours to figure it out. I decided to go with the Ten Meals.W: Why is that M: Well, I never eat breakfast and I often go away on weekends. So the ten meal plan gives me lunch and dinner each weekday at a fairly low price. And I won’t be paying for meals I don’t usually eat.W: And what about the weekend when you are on campus M: Well, there are often guests on campus at weekends. So they allow you to buy single meals on a walk-in basis on Saturdays and Sundays. The price per meal is much higher in that way. But I am away so much that it will still be less money for me to pay single prices on the weekends rather than sign up for the fourteen meals a week plan.W: Oh, I guess I’ll have to sit down and figure out my eating pattern so I can get the best deal.22. What’s the main feature of the new method of paying for meals