题目

用一张面积为251.2平方厘米的长方形纸围成一个圆柱的侧面，圆柱高8厘米。围成圆柱的体积最大是多少立方厘米？ 答案：【答案】628立方厘米【解析】根据圆柱的特征，长方形的长等于圆柱的底面周长，长方形的宽等于圆柱的高。用长方形的面积除以圆柱的高，求得圆柱的底面周长，进而求出圆柱的底面半径，然后求出底面积；然后根据圆柱的体积公式，用底面积乘高，即可得出圆柱的体积。251.2÷8÷3.14÷2＝31.4÷3.14÷2＝56．Recently，many people have begun to try a new way of doing shopping through the Internet．They are interested（31）C it．Why is it becoming more and more popular now？There are some （32）B．First，more and more people （33）Atheir own computers and their computers can be joined with the Internet．（34）Ait is possible for many of them to do shopping through the Internet．Second，shopping through the Internet can save them some money and （35）Btime．Third，they don't need to go to the （36）Dthemselves．Because of these good facts，few people refuse it．On the other hand，some people don't like this new way of （37）C．They are （38）Dabout the safety of shopping online．Customers can only （39）Bthe pictures of a product on the Internet．And they can't enjoy the pleasure of getting things at once．There are the reasons why they do not like it．But I think more and more people （40）Athis new kind of shopping in the future．31．A．onB．toC．inD．at32．A．excusesB．reasonsC．thingsD．methods33．A．haveB．hasC．hadD．having34．A．SoB．AndC．ButD．Because35．A．a number ofB．a lot ofC．a fewD．many36．A．libraryB．hospitalC．gymD．store37．A．eatingB．visitingC．shoppingD．cooking38．A．pleasingB．worryingC．pleasedD．worried39．A．drawB．seeC．showD．buy40．A．will likeB．likesC．likeD．liked