题目

碳碳双键加氢时总要放出热量，并且放出的热量与碳碳双键的数目大致成正比，实验测得下列反应的焓变数据 分析以上数据，不能得出的结论是 A．环已二烯分子内有二个碳碳双键      B．苯分子内有三个碳碳双键 C．苯是一种结构较为稳定的分子        D．上述三个加氢反应中苯放热最多 答案：BA typicalChinese Internet user is a young male who prefers instant messaging to e-mail, favors news, music and games sites and seldom makes online purchases（购物）．According to a study, about two-thirds of survey participants use the Internet for news — often entertainment-related — or for online games．About half download music and movies.They also tend to prefer instant messaging to e-mail, and they are depending on the Internet more frequently than before to communicate with others who have the same professions, hobbies and political interests．Online purchases still remain unpopular in China．Three-quarters of users surveyed have never bought anything over the Internet, and only 10 percent make purchases even once a month．Among those who do buy online, most pay for entertainment while others buy phone cards, or computer hardware or software.“Many people don’t trust the quality of goods bought online,” Guo said Wednesday．“If they buy it in a store and don’t like it, they can easily bring it back.”The survey was done in five major cities: Beijing, Shanghai, Guangzhou, Chengdu and Changsha．Results do not necessarily project countrywide because Internet use in rural areas is lower than in cities．Guo describes the typical netizenin the five cities surveyed as young, male, richer and more highly educated．Males make up two-thirds of the Internet community, and more than 80 percent of users are under 24．Among people ages 25 to 29, 60 percent to 80 percent go online.China has more than 100 million people online, second in the world to the United States.【小题1】A typical Chinese Internet user may be the one who _________.A．likes to send e-mailsB．likes to buy goods onlineC．likes to pay for entertainmentD．likes the games sites【小题2】Online purchases still remain unpopular in China mainly because _________.A．it is more difficult for sales returnsB．people haven’t computersC．it is not convenient to purchase on line D．all goods bought online are of low quality【小题3】Which of the following words fails to describe the typical netizens in the five cities?A．well educatedB．richerC．femaleD．young【小题4】According to the text, which of the following shows the right relation between online people and their ages?