单选题The party leader justified his subsequent reelection ______ that he had brought political stability and economic development to his country.

单选题 As a volunteer, John Apollos is losing weight—the old-fashioned way—by eating less. Apollos has lowered his daily caloric intake 25% over the past eight months. The fat, not surprisingly, has melted away. But that's not the real reason Apollos and the other participants in the program are eating only three-quarters of what they used to. The researchers are trying to determine whether restricting food intake can slow the ageing process and extend our life span. 'I feel better and lighter and healthier,' says Apollos. 'But if it could help you live longer, that would be pretty amazing.' The idea is counterintuitive: If we eat to live, how can starving ourselves add years to our lives? Yet decades of calorie-restriction studies involving organisms ranging from microscopic yeast to rats have shown just that. Last July a long-term study led by researchers at the University of Wisconsin, found that calorie restriction seemed to extend the lives of humanlike rhesus monkeys (恒河猴) as well. The hungry primates fell victim to diabetes, heart and brain disease and cancer much less frequently than their well-fed counterparts did. Scientists have suspected that calorie restriction could extend the life span of animals since at least 1935, when researchers at Cornell University noticed that severely food-restricted lab rats lived twice as long as normal ones and were healthier. Other investigators began exploring the idea and learned that the secret is not merely a matter of body weight. One theory is that a state of slight hunger acts as a mild but constant stressor that makes an organism stronger and more resistant to the ills of ageing. Taking in fewer calories also slows metabolism (新陈代谢), and some data indicate that humans with a slower metabolism live longer. But even if these theories are correct, simply defining the mechanism is not the same as identifying the molecular pathways behind it. If researchers could determine those pathways, they might be able to pharmacologically mimic (模仿) the effect of calorie restriction. That could be the ultimate benefit of the CALORIE study. 'Calorie restriction is pretty much the only thing out there that we know will not just prevent disease but also extend maximal life span,' says Dr. Marc Hellerstein, a nutritionist at the University of California.

单选题As a commander you should not ________ the soldiers to unnecessary danger.

单选题This passage is mainly concerned with ______.

单选题 电子出版(electronic publishing)原本只在科学领域较为普遍，但如今它有了更为丰富的内涵(connotation)。电子出版包括电子书、数字报纸、数字期刊、数字图书馆等等。目前大部分的电子出版都是通过互联网实现的，但也有一小部分电子出版物并不依赖互联网进行传播。速度是电子出版一项最突出的优势，同时，由于制作这些出版物无需印刷，可以节约大量的资源。一项市场调查显示，到2015年底，世界上近一半的期刊和报纸的出版将实现数字化。

单选题Daughter: I can't hear you, Mum. It's a really bad line. Mother: Sorry, dear. I said how are you? Daughter: Terrible, Mum. My back's killing me, and the house is a mess. Mother: ______ , darling. I'll come and help you clean the house.

单选题The number of cars, buses and bicycles in this city ______ to most of us.

单选题The man who never tries anything new is a(n)______on the wheels of progress.

单选题He had wanted a 25 % raise in pay, hut after talking to his boss, he decided that a 5% raise would have to ______.

单选题A: Women are still not fairly treated for all the equality demands. B: ______. I think you women have got everything important already.

单选题Remember to ask for a ______ of quality for these goods; otherwise they will not offer any maintenance. A. warranty B. promise C. certificate D. receipt

单选题She actually preferred a more {{U}}gregarious{{/U}} urban life style and the cultural attractions in a warmer clime.

单选题Scientists have been struggling to find out the reason behind blushing （脸红）。Why would humans evolve（进化） a 21__________ that puts us at a social disadvantage by 22__________ us to reveal that we have c

单选题W: Excuse me, do you have some change for a dollar? M:______

单选题The Rose Bowl parade (takes place) every year (in) Pasadena (in) (New Year's Day).

单选题Rural communities are usually more______in their child-rearing methods, while in the town there is more variety.

单选题The remedies proposed for dealing with the situation ore only ______ promises for action for the future.

单选题Shop-assistant: Can I help you? Customer: Yes, I'd like to try these shoes in size 4, please? Shop-assistant: Yes, just a moment ... I'm sorry but we've only got them in four and a half. ______?

单选题 在指南针发明以前，人们在茫茫大海上航行，只能靠太阳和星星的位置辨认方向，如果遇上阴雨天，就会迷失方向。是中国人发明的指南针帮助解决了这个难题。指南针是指示方向的仪器。早在战国时期(the Warring States Period)(475 BC-221 BC)，中国人就发现了磁石能够指示南北的特性，并根据这种特性制成了指示方向的仪器——司南(sinan)。到了宋代，人们制成了“罗盘”(luopan)。指南针的发明，给航海事业带来了划时代的影响，世界航运史也由此翻开了新的一页。

单选题The fact that the golden eagle usually builds its nest on some high cliffs ______ it almost impossible to obtain the eggs or the young birds.