Big schoolbags have been a serious problem for students for a long time. Maybe your schoolbag is too         to carry, and it troubles you a lot        you want to find a book out to read. Now an e-textbook will         you.
It is said that e-textbooks are going to be        in Chinese middle schools. An e-textbook, in fact, is a small          for students. It is much        than a usual schoolbag and easy to carry. Though it is as small as a book, it can       all the materials (材料) for study. The students can read the text page by page on the        , take notes with the pointer (屏写笔). Or even “        ” their homework to their teachers by sending emails. All they have to do is to press a button.
Some people say e-textbooks are good, but some say they may be        for the students' eyes. What do you think of it?
A. light             B. heavy        C. useful        
A. till              B. after            C. when
A. trouble           B. prevent       C. help    
A. used              B. kept             C. invented 
A. computer          B. radio            C. pen      
A. heavier           B. lighter          C. cheaper      
A. hold              B. build            C. discover     
A. blackboard            B. desk           C. screen       
A. find out          B. hand in          C. get back     
A. helpful              B. famous       C. bad