A、They get more freedom. B、They encounter more pressure. C、They shoulder more social responsibilities. D、They are required to do

　　As we all know, there are many differences lying between high school and college. For some students, one of the biggest differences is the amount and depth of research that is required for research papers. (22) College professors expect students to be quite adept at researching, and for some students, this is a big change from high school. This is not to say that high school teachers don’t do a great job to prepare their students for college level research—quite the contrary! (23) Teachers in high school play a tough and essential role in teaching students how to research and write, and college professors simply require students to take that skill to a new level. For example, you may soon discover that many college professors won’t accept encyclopedia (百科全书) articles as research sources. Encyclopedias are great for finding a compact, informative accumulation of research on a specific topic. They are a great resource for finding the basic facts, (24) but they are limited when it comes to offering interpretations of the facts. (25) Professors require students to dig a little deeper than that, accumulate their own evidence from broader sources, and form opinions about their sources as well as the specific topics. For this reason, college-bound students should become familiar with the library and all its terms, rules and methods. They should also have the confidence to venture outside the comfort of the local public library and explore more diverse resources.
　　22.  What is the big change from high school to college for some students?
　　23.  What do high school teachers usually do according to the passage?
　　24.  Why shouldn’t encyclopedias be used as research sources?
　　25.  What do professors ask students to do when doing research?