问题 选择题

留心处处皆学问,世事洞明即文章.关于自行车的科学知识,下列说法正确的是(  )

A.车轮外胎表面凹凸不平是为了减小摩擦,可以使自行车行驶得更快

B.座垫呈马鞍型,它能够增大座垫与人体的接触面积以减小臀部所受压强

C.自行车在紧急刹车时,根据惯性,只捏前刹比同时捏前后刹更安全

D.需转动的地方,在轴与轴套之间装滚珠轴承变滚动为滑动

答案

A、自行车车轮的外表面都有凹凸不平的花纹,是在压力一定时,增大接触面的粗糙程度来增大摩擦力,故A错误.

B、人坐在马鞍型的自行车坐垫上,压力一定,受力面积增大,减小了车垫对臀部的压强,臀部感到比较舒服.故B正确.

C、高速骑行时,如果只将前闸捏死,自行车很可能会在惯性作用下后轮离地,甚至翻到前面去.故C错误.

D、在转盘内安装滚珠轴承,用滚动摩擦代替滑动摩擦;属于减小摩擦;故D错误.

故选B.

阅读理解

请阅读下列应用文及相关信息,并按照要求匹配信息。请在答题卡上将对应题号的相应选项字母涂黑。

以下是请求帮助者的资料:

A.  As we know, the 2008 Olympic Games will be held in Beijing and many people from other countries will come to visit China. The taxi drivers in Dongfeng Taxi Company think the way to show kindness is to be able to greet the foreigners in their languages. They need someone who can teach them languages and the best time is at night when they are not so busy.

B.  Tom is so addicted to on-line games that he cannot concentrate on his study like before. Now he often misses school in order to play games, thus telling lies to his teachers and parents again and again. Though he realizes what he does is wrong, he just can’t stop it. How badly he needs someone’s help.

C.  Mane, a 44-year-old single mother of three, has to walk two miles to the nearest supermarket twice a week because she doesn’t know which bus to take. What’s worse, since she does not know words, she can not write out a shopping list. Also, she can only recognize items by sight, so if the product has a different label, she will not recognize it as the product she wants.

D.  "Helping Hand"Organization will hold an event to help the starving children in Africa. The event starts in August and those taking part in will go without food for 30 hours. In this way, it is expected that money will be raised for the poor children.

E.  "Green Earth" cares a lot for the animals in danger. Still many people in the world don’t know much about the importance of animal protecting. This summer vacation a lot of events will be organized to call on people to live in harmony with our earth.

F.  A group of young children in a remote village in southwest China are in great need of teachers. Because of the low salary, many teachers came and then went. The villagers hope to have a teacher who can stay for at least a year, because they know knowledge can make a difference to the children’s future.

以下是乐于提供资助的人员信息介绍。请匹配他们与所对应的资助对象。

小题1:Stephen:  Last summer I went through a training program and became a literacy volunteer. When I began to discover what other people’s lives were like because they could not read, I realized the true importance of reading.

小题2:Ben:  After graduation, I don’t want to apply for a job at once Instead, I plan to spare one year to help those who need help most and try my best to improve their lives. You know, education is essential to poverty relief and at the same time I’ll get valuable experience for my future career.

小题3:Susan:  I’m a girl from England and have studied French for years. I’m here in Beijing University studying Chinese. I like China as it is full of mysteries. So I hope the voluntary work will help me to get in touch with Chinese people and get to know about China. Although my study is busy, I can be free at night and at the weekends.

小题4:Tim:  Since I myself have overcome a lot of difficulties in my life, I understand young people’s problems and I know how to listen patiently to others and offer some advice. I’m working now in the daytime so I can only spend two to three hours a day at night helping others.

小题5:Lisa:  I burst into tears when I saw those children in a TV program. What a sight. They are only bone and skin left. What’s worse, every day the children are dying because of lack of food. I realized how lucky I am with enough food and a good chance to get education. The summer vacation is coming and I hope I can do something for them.

单项选择题