A、More than 15 pounds. B、More than 20 pounds. C、Less than 2 pounds. D、Less than 15 pounds. D短文中提到，研究发现，在大学生活的前两年时间里，每个学生的体重平均增加3

Everyone has heard warnings about the "freshman 15." But is it true that many college students gain 15 pounds during their first year at school? Recent studies find that some first-year students are indeed likely to gain weight—but it might not be the full freshman 15, and it may not all happen during freshman year. That might sound like good news, but it’s not.(15)Doctors are concerned that students who gradually put on pounds are establishing a pattern of weight gain that could lead to trouble if it continues.(16)Studies show that students on average gain three to ten pounds during their first two years of college. Most of this weight gain occurs during the first semester of freshman year. College offers many temptations. You’re on your own and free to eat what you want, when you want it. You can eat dinners of French fries and ice cream in the dining hall, and can have an "additional meal" during late-night study. In addition, you may not get as much exercise as you did in high school. College is also a time of change,(17)and the stress of adjusting to school can trigger overeating. People sometimes eat in response to anxiety, homesickness, sadness, or stress, and all of these can be part of adapting to being away at school.
15. What kind of students are doctors concerned about?
16. How many pounds do students usually gain during the first two years at college?
17. What causes stress in some first-year college students?