B. traveling　　C. doing social investigation　　D. other ways　　From the two charts, we can see that in the past ten years the students who go traveling and do social investigations during vacations have increased greatly while those who stay at home have decreased a lot.　　There are several reasons for the changes. Firstly, with the development of economy, many people have become better off. Students can get financial support from their parents for traveling. Secondly, tourism has greatly developed over the past ten years. Many new scenic spots have been built and exploited. In addition, the students today are expected and encouraged to participate in facing the real world. In this way they can obtain the necessary experiences required when they go job-hunting upon graduation.　　From the changes in the charts, we can predict that more and more college students will make their vacations interesting and worthwhile by going to the outside world instead of staying at home.