55. What did the joint study find about the MOOCs several years ago?

30. The author expresses his concern at the end of the passage that

29. What is the author＇s view of face-to-face communication?

28. Wpat does the author say about the advantage of chatting online?

27. What does the author mean by "crossing these bridges" (Line 7, Para. 2)?

26. The author thinks that after school teens should spend time(

25. What solution does Rosen offer?

24. What has Rosen found in his experiments about students not allowed to use cellphones?

23. Larry Rosen advises other professors not to follow Duncan＇s lead because

22. What experiment did Duncan carry out to reduce cellphone use in class?

21. What is the finding reported in Doug Duncan＇s published paper?