单选题You ______ Mark anything. It was none of his business. A. needn't have told B. needn't tell C. mustn't have told D. mustn't tell

单选题The average young American now spends practically every waking minute—except for the time in school, though reluctantly—using a smart phone, computer, television or other electronic devices, according to a new study. Those ages 8 to 18 spend seven and a half hours a day with such devices, compared with less than six and a half hours five years ago. And that does not count the hour and a half that youths spend texting, or the half hour they talk on their cellphones. And because so many of them are multitasking—say, surfing the Internet while listening to music—they pack on average nearly 11 hours of media content into that seven and a half hours. The study's findings shocked its authors, who had concluded in 2005 that use could not possibly grow further, and confirmed the fears of many parents whose children are constantly tethered to media devices. ① It found, moreover, that heavy media use is associated with several negatives, including behavior problems and lower grades. Dr. Michael Rich, a pediatrician at Children's Hospital Boston who directs the Center on Media and Child Health, said that with media use so ubiquitous, it was time to stop arguing over whether it was good or bad and accept it as part of children's environment, "like the air they breathe, the water they drink and the food they eat. " Contrary to popular wisdom, the heaviest media users reported spending a similar amount of time exercising as the light media users. Nonetheless, other studies have established a link between screen time and obesity. While most of the young people in the study got good grades, 47 percent of the heaviest media users—those who consumed at least 16 hours a day—had mostly C's or lower, compared with 23 percent of those who typically consumed media three hours a day or less. The heaviest media users were also more likely than the lightest users to report that they were bored or sad, or that they got into trouble, did not get along well with their parents and were not happy at school. The study could not say whether the media use causes problems, or, rather, whether troubled youths turn to heavy media use. "This is a stunner," said Donald F. Roberts, one of the authors of the study. "In the second report, I remember writing a paragraph saying we've hit a ceiling on media use, since there just aren't enough hours in the day to increase the time children spend on media.② But now it's up an hour. /

单选题The old man said that the city ______ much since he came here. A. changed B. has changed C. is changing D. had changed

单选题The government's new cyber-security officials yesterday asked telecommunications companies for help in building at government computer network that would have "no risk of outside penetration" — a task some computer security consultants say is nearly impossible. Plans for the private network, called Govnet, hinge on whether a reliable network infrastructure can be built at an affordable price, officials said. Computer system consultants said they could not estimate how much the network would cost because of the government's enormous size and security needs. Richard Clarke, who was appointed special adviser to the president for cyberspace security this week, said he believes a more reliable system can be built. Ninety percent of available fiber-optic space is unused and fairly inexpensive to obtain, he said. Govnet is part of a plan Clarke announced earlier this week "to secure our cyberspace from a range of possible threats, from hackers to criminals to terrorist groups, to foreign nations, which might use cyber-war against us in the future". Govnet would be completely independent from the Internet to help keep out hackers and viruses, according to the government's plan. The request from the General Services Administration asks that telecommunications companies submit proposals about how the network could be built, how much it would cost, and how long it would take to construct. This year, the current network has been breached by hackers, computer worms and viruses. The system was also roughed up by the "Code Red" computer worm and an attack program called "I Love You". The viruses affected thousands of government computers. Last year a report by the General Accounting Office, an internal government watchdog, found weaknesses in the computer network that could allow terrorists or hackers to "severely damage or disrupt national defense or vital public operations or steal sensitive data". Clarke said the government's current virtual private network is vulnerable to viruses and denial of service attacks that Govnet would make more difficult to execute. An internal network, such as the Govnet proposal, is worth investigating but will probably fall to sophisticated hackers, said Amit Yoran, chief executive of the security-services company Riptech Inc. and a former information-security program director at the Defense Department. "It is probably more feasible to implement and strongly enforce global security postures and practices rather than go out and purchase new assets," Yoran said. "Once someone is able to get in, they will find a weak link. When you have a network the size of the government's there will be weak links. Someone will get in./

单选题{{B}}SECTION A CONVERSATIONS{{/B}} {{I}} In this section you will hear several conversations. Listen carefully and then answer the questions that follow.{{/I}} {{I}} Questions 1 to 3 are based on the following conversation. At the end of the conversation, you will be given 15 seconds to answer the questions. Now, listen to the conversation.{{/I}}

单选题Which of the following italicized phrases indicates PURPOSE?

单选题Researchers______ that genes may determine the strength of the immune system which could help explain how an infectious disease could have a hereditary link. A. speculate B. estimate C. evaluate D. anticipate

单选题Questions 1 to 3 are based on the following conversation. At the end of the conversation, you will be given 15 seconds to answer the questions.

单选题His plan is carefully prepared and full of details, so it is a very ______ one.A. elaborateB. refinedC. ambitiousD. complex

单选题If only I ______ how to operate a computer. A. learned B. have learned C. would learn D. had learned

单选题{{I}} Questions 24 and 25 are based on the following news. At the end of the news item, you will be given 10 seconds to answer the questions. Now, listen to the news.{{/I}}

单选题{{I}} Questions 27 to 28 are based on the following news. At the end of the news item, you will be given 10 seconds to answer the questions. Now listen to the news.{{/I}}

单选题Sense and Sensibility is a good movie by any standard; ______ it should rank high on any list of romance. A. consistently B. consequently C. invariably D. subsequently

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单选题The author believes that our knowledge of social systems is more secure than that of physical system because ______.

单选题Which one might be true according to what you hear?

单选题In "We listened eagerly, for he brought news of our families", "for" is used to indicate ______.

单选题Which of the following is mentioned in the passage ?

单选题 Questions 24 and 25 are based on the following news. At the end of the news item, you will be given 10 seconds to answer the questions. Now, listen to the news.