单选题What lesson might the PR industry take from Ted Turner of CNN?

单选题According to the first paragraph, pictures of animals were painted on the walls of caves because ______.

单选题_______ in the color of sea water from blue to green seem to be caused by high or low concentration of salt.

单选题The most pressing nuclear energy issue is the disposal of nuclear waste. Even if all the reactors in existence were completely safe to operate, there would still be unsolved issue of what to do with the waste from generating electricity by means of nuclear energy. Those who claim that they feel comfortable with nuclear energy are, none the less, concerned about waste disposal methods. Seven states, including California, have put the building of nuclear plants on hold until legislators are convinced that there is a safe way to dispose of the radioactive waste from the plants. In the meantime, pools of liquid waste and piles of solid waste from private industry and governmental bomb production grow. Since 1962, the volume of radioactive waste produced by the nuclear power industry has amounted to about 4,300 cubic meters. By the end of the twentieth century, if production continues at the same rate, there will be 40,000 cubic meters of nuclear waste. Power plants and bomb-making are not the only sources of waste. Uranium mining and milling operations have dumped 24 million metric tons of radioactive tailing wastes at dumping sites around the nation. At places where uranium is currently milled, there is another 100 million metric tons of tailings. Uranium tailings are solid materials in the slurry (or watery mixture) of depleted ore-bearing rock, chemicals, and liquids that result from milling. Usually, the slurry is piped to holding ponds. When a uranium mill goes out of business, the ponds are left to evaporate , uncovering piles of dried tailings. Uncovered piles of tailings give off radioactive radon gas. Once in the air, the gas finds its way into the water supply and the food chain. Consequently, many nuclear experts agree that uranium mill tailings may be more dangerous than high-level radioactive wastes from reactors and bombs.

单选题Many once prosperous northern mill towns have _________ as industry has moved to the South.

单选题Many people view retirement as a time to stop working. But new research shows that people who take on full- or part-time jobs after retirement have better health. The finding is based on data collected from 12,189 men and women over a 6-year period. The participant.,;, who were from ages 51 to 61 at the start of the study, answered questions about their employment history, experiences after retirement and their physical and mental health. Researchers from the University of Maryland found that men and women who kept working after retirement had fewer major diseases or disabilities than those who quit work, according to the study. Retirees benefited whether the work was a full- or part-time job, self-employment or temporary. While working after retirement is good for you, the data also suggest that retirees shouldn't take on just any job. Among those who kept working, the retirees who found work related to their previous careers had the best mental health. The study authors speculated (猜测) that working outside a person's main area of expertness might lead to more stress. Other studies have also supported the idea that working after retirement is good for you. A long-term study of 1,000 men and women born in 1920 suggested that working after retirement was associated with living longer. The participants joined the study at age 70 and were tracked for 14 years by researchers from the Hadassah Hospital Mount Scopus in Jerusalem. After controlling for individuals' health at the beginning of the study, the researchers found that whether a person was still alive after 12 years was strongly associated with whether they had been actively working or were fully retired. Among the 1,000 people studied, those who continued to work at age 70 and beyond were 2.5 times as likely to be alive at age 82 as those who had retired and were not working at the beginning of the study. Another study showed that losing a job at an older age can be destructive to health. Yale researchers followed 4,220 workers, ages 51 to 61, for 6 years. During the study period,457 workers lost their jobs. Being laid off close to retirement increased the risk for stroke by three times, according to the study published in the American Journal of Industrial Medicine.

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单选题Why didn't the government's expansion program work very well?

单选题A．Inhisbuilding'sparkinglot.B．Neartheentranceofapark.C．Atastreetcorner.D．Ataparkingmeter.

单选题Male lions are rather reserved about expending their energy in hunting. More than three-quarters of kills are made by lionesses. Setting off (1) dusk on a hunt, the lionesses are in (2) , tensely scanning ahead, the young lions fall playfully behind, and the (3) bring up the rear, walking slowly, their massive (4) nodding with each step as if they (5) with the whole matter. But (6) may have survival value. (7) lionesses busy hunting, the males (8) as guards for the young, (9) them particularly from hyenas (土狼). Hunting lionesses have learnt to take advantage of their (10) . Darkness (11) them with cover, and at dusk they (12) wait near animals they want to kill (13) their outlines blend into the surroundings. Small prey (猎物) present lions with no (14) . They are simply grabbed with the paws. A (15) technique is used with (16) animals, such as wildebeest ( 角马). Usually a lioness pulls her prey down (17) running up behind (18) , and then seizes it (19) the throat. Or she may place her mouth over the muzzle (动物之鼻口) of a downed animal, (20) it.

单选题Cellular phones are wireless mobile phones that ______ and receive computer-controlled radio signals.