读“地震波速度与地球内部构造图”，回答下列问题。图中各层名称：B是（），C是（）。 发布时间：2019-01-31 01:15 │ 来源：www.tikuol.com 题型：填空题 案例分析题 问题： 读“地震波速度与地球内部构造图”，回答下列问题。图中各层名称：B是（），C是（）。
题型：填空题 案例分析题 完形填空 Big schoolbags have been a serious problem for students for a long time.Maybe your schoolbag is too __26__ to carry, and it troubles you a lot __27__ you want to find a book out to read. Now an etextbook will __28__ you. It is said that etextbooks are going to be __29__ in Chinese middle schools.An etextbook, in fact, is a small __30__ for students.It is much __31__ than a usual schoolbag and easy to carry. Though it is as small as a book, it can __32__ all the materials (材料) for study.The students can read the text page by page on the __33__， take notes with the pointer (屏写笔). Or even “__34__” their homework to their teachers by sending emails. All they have to do is to press a button. Some people say etextbooks are good, but some say they may be __35__ for the students' eyes. What do you think of it? 26.A.light 27.A.till 28.A.trouble 29.A.used 30.A.TV 31.A.heavier 32.A.hold 33.A.blackboard34.A.find out 35.A.helpful B. heavy B. after B. preventB. kept B. radio B. lighterB. build B. desk B. hand inB. famous C. useful C. before C. help C. inventedC. pen C. cheaper C. discoverC. screen C. get backC. good D. comfortable D. when D. understand D. lent D. com puter D. brighter D. practice D. card D. give back D. bad 查看答案
