题目

点电荷与带电金属板之间的电场和电场线分布如图所示，对此电场的分析，下列说法正确的是（） A . 金属板的电势是正中间（正电荷的正下方）最高，向两边依次降低 B . 金属板上表面的电场线都垂直于金属板表面 C . 因为a点的电势高于b点的电势，故把一正点电荷从a点沿某一路径运动到b点，电场力一定全程做正功 D . 置于a点的负电荷的电势能大于把它置于b点所具有的电势能 阅读理解。 　　Can you imagine a world without the Internet?It's surprising to think about it． 　　Now, China has more than 162 million Internet users, according to the China Internet Network Information Centre．This is the second highest number of user in the world after the United States．Today, 66％of Chinese“netizens(网民)”are teenagers．“They spend about thirteen hours every week online,”said Qian Hulin, an Internet expert(专家)．Doctor Song in Beijing Xuanwu Hospital said about 14％ of Chinese netizens who are teens often lasted over ten hours to play online games． 　　The main reasons why teenagers surf the Web are to search for information, to communicate with others and to have fun．On the Internet, teenagers can find out almost anything．And surfing the Web can help students with their homework and widen their knowledge． 　　Li Dong, a teacher at No．41 Middle School in Shijiazhuang, likes her students to use the Internet．“When we talk in class, students who surf the Net usually know more background information than the others,”she said． 　　In addition, people can use the Internet to write letters or stories and send emails．Many teens keep in touch with their friends online．It is cheaper than phoning somebody far away and also much quicker． (1) ________ has the most Internet users in the world according to the article． [　　] A． China B． America C． Canada D． Russia (2) There are about ________ Chinese netizens to surf about 13 hours every week． [　　] A． 107 million old B． 22.7 million old C． 107 million young D． 22.7 million young (3) Song said some teenagers continued ________ more than ten hours． [　　] A． playing online games B． searching for information C． chatting with their friends D． sending emails to others (4) Li Dong in No．41 Middle School likes her students to use the Internet because she ________． [　　] A． thinks surfing the net can help students spend less time on homework B． thinks her students can get more background information than the others C． wants her students to talk to her about their hobbies and interests D． wants to know what her students do and think about at home (5) Which way is the cheapest and quickest to learn something about friends far away? [　　] A． Giving them a call． B． Going to see them． C． Writing a letter to them． D． Sending emails to them．