A、The cost of their e-textbooks. B、The improved technology. C、The altering of their study habits. D、The convenience for their us

Online versions are now available for many of the most popular college textbooks. B-textbooks can cost half the price of a new print textbook. (33)But e-textbooks do not sell well for students usually lose access after the end of the term. And the books cannot be placed on more than one device, so they are not easy to share.
    So what do students think of e-textbooks? Administrators at Northwest Missouri State University wanted to find out. Earlier this year they tested them with five hundred students in twenty classes.
    The university provides laptop computers to all its full-time students and rent them textbooks to save money. The school aims to save even more by moving to e-textbooks. The students in the survey reported that downloading the books from the Internet was easy. They liked the idea of carrying lighter backpacks. And 56% said they were better able to find information. But most found that using e-textbooks did not change their study habits. And 60% felt they read more when they were reading on paper. In all, almost half the students said they still liked physical textbooks better. (34)But the survey found that cost could be a big influence. 55% said they would choose e-textbooks if using them meant their textbook rental fee would not increase.
    Roger Holzen at Northwest Missouri State says that(35)the e-textbooks now available are disappointing because the majority are not interactive. He thinks growth will come when more digital books include video, activities, games and other ways to interact with the information. The technology is improving. But for now, most of the books are just words on a screen.
33. Q: According to the speaker, why don’t e-textbooks sell well?
34. Q: According to the survey, what might be an influential element for students to choose e-textbooks?
35. Q: What does Roger Holzen think of the current e-textbooks?