A、Watching TV. B、Listening to music. C、Reading magazines. D、Playing computer games. B短文最后提到，在被问及哪一种活动最难放弃长达一周的时间时，48％的受访者认为是听音乐，

According to a survey on reading conducted in 2001 by the U. S. National Education Association, young Americans say reading is important, more important than computers and science.(20)Over 50% of the 12- to 18-year-olds interviewed said they enjoy reading a lot. 79% find it stimulating and interesting. And 87% think it is relaxing. About 68% of those surveyed disagree with the opinion that reading is boring or old-fashioned. Over half the teenagers interviewed said they read more than ten books a year. The results also showed that middle school students read more books than high schoolers.(21)Over 66% of teens like to read fiction, such as novels and stories. Only 26% were interested in non-fiction, such as history books. 64% of students listed reading stories about people my own age as their favorite topic.(21)Mysteries and detective stories came second on the list at 53% . Just under 50% said they were interested in reading about their own culture and tradition. Of the teenagers who participated in the survey, 49% said that libraries are where they get most of their books. However, many complain that their school libraries do not have enough up-to-date interesting books and magazines. Even though many teenagers in the U. S. enjoy reading, they still have other interests.(22)When asked which activity would be the most difficult to give up for a week, 48% said listening to music. TV would be difficult to give up for 25% of those surveyed.
20. What does the survey on teenager reading show?
21. What books are most popular among teenagers according to the survey?
22. What activity do teenagers find the most difficult to give up for a week?