A、Professors and researchers. B、Foreign guests and students. C、News people and entertainers. D、Professors and leaders. C文中谈到，“常常

May and June are the months when most American colleges and universities hold their graduation ceremonies. These ceremonies are a time for family and friends to gather and celebrate a student’s completion of an academic degree. Most ceremonies are traditional. The students wear caps and gowns over their clothing. One by one, their names are called. They go to the front, shake hands with school officials and receive a document of some kind. But first they must sit and listen to speeches. Colleges and universities often invite famous guests or former students who have been successful. Schools often want speakers to comment on world events. This Saturday, for example, Senator Hillary Rodham Clinton will speak at the graduation ceremony at the Rensselaer Polytechnic Institute in Troy, New York. News people are often invited to speak at graduations. So are entertainers. Actor John Lithgow, a 1967 graduate of Harvard, will speak at the university on June 9th. Then there are speakers like Jon Stewart. He entertains by making fun of the news. His popular program, "The Daily Show," appears on Comedy Central on cable television. Last year, Jon Stewart spoke at the College of William and Mary in Williamsburg, Virginia. He graduated from there in 1984. He did offer some serious advice. He said: "College is something you complete. Life is something you experience. So don’t worry about your grade, or the results or success. Success is defined in various ways, and you will find it... Love what you do. Get good at it."
22. When do most American universities hold their graduation ceremonies?
23. Who are often invited to speak at the graduation ceremonies?
24. Which university did the actor John Lithgow graduate from?
25. What advice did Jon Stewart give at the ceremony of the College of William and Mary?