完形填空Big schoolbags have been a serious problem for students

完形填空
Big schoolbags have been a serious problem for students for a long time.Maybe your schoolbag is too 46 to carry,and it troubles you a lot 47 you want to find a book out to read,Now an e-textbook will 48 you.
It is said that e-textbooks are going to be 49 in Chinese middle schools.An e-textbook,in fact,is a small 50 for students.It is much 51 than a usual schoolbag and easy to carry.Though it is as small as a book,it can 52 all the materials（材料）for study.The students can read the text page by page on the 53 ,take notes with the pointer（屏写笔）.Or even “54 ”their homework to their teachers by sending e-mails.All they have to do is to press a button.
Some people say e-textbooks are good.but some say they may be 55 for the students’eyes.What do you think of it?
46.A.light B.heavy C.useful D.comfortable
47.A.till B.after C.before D.when
48.A.trouble B.prevent C.help D.understand
49.A.used B.kept C.invented D.lent
50.A.TV B.radio C.pen D.computer
51.A.heavier B.lighter C.cheaper D.brighter
52.A.hold B.build C.discover D.practise
53.A.blackboard B.desk C.screen D.card
54.A.find out B.hand in C.get back D.give back
55.A.helpful B.famous C.good D.bad