单选题设f(x)是连续的偶函数，则其原函数F(x)一定是______．

单选题如果灵活性偏好曲线接近水平，意味着（ ）

单选题It's no surprise that Jennifer Senior's insightful, provocative magazine cover story, “I love My Children, I Hate My Life,” is arousing much chatter–nothing gets people talking like the suggestion that child rearing is anything less than a completely fulfilling, life-enriching experience. Rather than concluding that children make parents either happy or miserable, Senior suggests we need to redefine happiness: instead of thinking of it as something that can be measured by moment-to-moment joy, we should consider being happy as a past-tense condition. Even though the day-to-day experience of raising kids can be soul-crushingly hard, Senior writes that “the very things that in the moment dampen our moods can later be sources of intense gratification and delight.” The magazine cover showing an attractive mother holding a cute baby is hardly the only Madonna-and-child image on newsstands this week. There are also stories about newly adoptive–and newly single–mom Sandra Bullock, as well as the usual “Jennifer Aniston is pregnant” news. Practically every week features at least one celebrity mom, or mom-to-be, smiling on the newsstands. In a society that so persistently celebrates procreation, is it any wonder that admitting you regret having children is equivalent to admitting you support kitten-killing ? It doesn't seem quite fair, then, to compare the regrets of parents to the regrets of the children. Unhappy parents rarely are provoked to wonder if they shouldn't have had kids, but unhappy childless folks are bothered with the message that children are the single most important thing in the world: obviously their misery must be a direct result of the gaping baby-size holes in their lives. Of course, the image of parenthood that celebrity magazines like Us Weekly and People present is hugely unrealistic, especially when the parents are single mothers like Bullock. According to several studies concluding that parents are less happy than childless couples, single parents are the least happy of all. No shock there, considering how much work it is to raise a kid without a partner to lean on; yet to hear Sandra and Britney tell it, raising a kid on their “own” (read: with round-the-clock help) is a piece of cake. It's hard to imagine that many people are dumb enough to want children just because Reese and Angelina make it look so glamorous: most adults understand that a baby is not a haircut. But it's interesting to wonder if the images we see every week of stress-free, happiness-enhancing parenthood aren't in some small, subconscious way contributing to our own dissatisfactions with the actual experience, in the same way that a small part of us hoped getting “ the Rachel” might make us look just a little bit like Jennifer Aniston.

单选题当两种商品X、Y的效用函敦为Y(X．Y)=XY时，下列哪一种效用函数描述了相同的偏好次序?

单选题在一次魔术表演中，从七位魔术师G、H、K、L、N、P和Q中选择六位上场表演，表演时分成两队：1队和2队。每队有前、中、后三个位置，上场的魔术师恰好每人占一个位置，魔术师的选择和位置安排必须符合下列条件： (1)如果安排G或H上场，他们必须在前位； (2)如果安排K上场，他必须在中位； (3)如果安排L上场，他必须在1队； (4)P和K都不能与N在同一个队； (5)P不能与Q在同一个队； (6)如果H在2队，则Q在l队的中位。

单选题Every second, 1 hectare of the world's rainforest is destroyed. That's equivalent to two football fields. An area the size of New York City is lost every day. In a year, that adds up to 31 million hectares—more than the land area of Poland. This alarming rate of destruction has serious consequences for the environment; scientists estimate, for example, that 137 species of plant, insect or animal become extinct every day due to logging. In British Columbia, where, since 1990, thirteen rainforest valleys have been clearcut, 142 species of salmon have already become extinct, and the habitats of grizzly bears, wolves and many other creatures are threatened. Logging, however, provides jobs, profits, taxes for the government and cheap products of all kinds for consumers, so the government is reluctant to restrict or control it. Much of Canada's forestry production goes towards making pulp and paper. According to the Canadian Pulp and Paper Association, Canada supplies 34% of the world's wood pulp and 49% of its newsprint paper. If these paper products could be produced in some other way, Canadian forests could be preserved. Recently, a possible alternative way of producing paper has been suggested by agriculturalists and environmentalists: a plant called hemp. Hemp has been cultivated by many cultures for thousands of years. It produces fiber which can be made into paper, fuel, oils, textiles, food, and rope. For many centuries, it was essential to the economies of many countries because it was used to make the ropes and cables used on sailing ships; colonial expansion and the establishment of a world wide trading network would not have been possible without hemp. Nowadays, ships' cables are usually made from wire or synthetic fibres, but scientists are now suggesting that the cultivation of hemp should be revived for the production of paper and pulp. According to its proponents, four times as much paper can be produced from land using hemp rather than trees, and many environmentalists believe that the large-scale cultivation of hemp could reduce the pressure on Canada's forests. However, there is a problem: hemp is illegal in many countries of the world. This plant, so useful for fiber, rope, oil, fuel and textiles, is a species of cannabis, related to the plant from which marijuana is produced. In the late 1930s, a movement to ban the drug marijuana began to gather force, resulting in the eventual banning of the cultivation not only of the plant used to produce the drug, but also of the commercial fiber-producing hemp plant. Although both George Washington and Thomas Jefferson grew hemp in large quantities on their own land, any American growing the plant today would soon find himself in prison—despite the fact that marijuana cannot be produced from the hemp plant, since it contains almost no THC (the active ingredient in the drug). In recent years, two major movements for legalization have been gathering strength. One group of activists believes that ALL cannabis should be legal—both the hemp plant and the marijuana plant—and that the use of the drug marijuana should not be an offense. They argue that marijuana is not dangerous or addictive, and that it is used by large numbers of people who are not criminals but productive members of society. They also point out that marijuana is less toxic than alcohol or tobacco. The other legalization movement is concerned only with the hemp plant used to produce fiber; this group wants to make it legal to cultivate the plant and sell the fiber for paper and pulp production. This second group has had a major triumph recently: in 1997, Canada legalized the farming of hemp for fiber. For the first time since 1938, hundreds of farmers are planting this crop, and soon we can expect to see pulp and paper produced from this new source.

单选题若某商品的需求曲线为一条向右下方倾斜的直线，当厂商由高到低逐渐降低销售价格时( )。

单选题某国家领导人要在连续6天(分别编号为第一天、第二天……第六天)内视察6座工厂F、G、H、J、O和R，每天只视察一座工厂，每座工厂只视察一次。视察时间的安排必须符合下列条件： (1)视察F在第一天或第六天。 (2)视察J的日子比视察Q的日子早。 (3)视察Q恰在视察R的前一天。 (4)如果视察G在第三天，则视察O在第五天。

单选题在某大型理发店内，所有的理发师都是北方人，所有的女员工都是南方人，所有的已婚者都是女员工，所以，所有的已婚者都不是理发师。 下面哪一项如果为真，将证明上述推理的前提至少有一个是假的?

单选题设随机变量X的概率密度为，则其分布函数______．A．B．C．D．

单选题圈养动物是比野生动物更有意思的研究对象。因此，研究圈养动物能够比研究野生动物学到更多的东西。 上面的论证依赖于下面哪一个假设?

单选题在下面哪一种经济体中，货币政策将会对产出产生最大的影响。( )

单选题When anyone opens a current account at a bank, he is lending the bank money. He may (1) the repayment of the money at any time, either (2) cash or by drawing a check in favor of another person. (3) , the banker-customer relationship is that of debtor and creditor who is (4) depending on whether the customer's account is (5) credit or is overdrawn. But, in (6) to that basically simple concept, the bank and its customer (7) a large number of obligations to one another. Many of these obligations can give (8) to problems and complications but a bank customer, unlike, say, a buyer of goods, cannot complain that the law is (9) against him. The bank must (10) its customer's instructions, and not those of anyone else. (11) , for example, a customer opens an account, he instructs the bank to debit his account only in (12) of checks drawn by himself. He gives the bank (13) of his signature, and there is a very firm rule that the bank has no right or (14) to pay out a customer's money (15) a check on which its customer's signature has been (16) It makes no difference that the forgery may have been a very (17) one: the bank must recognize its customer's signature. For this reason there is no (18) to the customer in the practice, (19) by banks, of printing the customer's name on his checks. If this (20) Forgery, it is the bank that will lose, not the customer. (254 words)

单选题每个委员在委员会中工作两年，委员会由4人组成，其中2名成员来自4位法官——F、G、H、I，另外2名成员来自3位科学家——V、Y、Z。每年，该委员会有1名成员做主席。第一年做主席的成员在第二年必须退出该委员会。在第二年做主席的人在第一年必须是该委员会的成员。该委员会成员必须满足下面的条件： (1)G和V不能在同一年成为该委员会的成员； (2)H和Y不能在同一年成为该委员会的成员； (3)每一年，I和V中有且只有一位做该委员会的成员。

单选题假定政府规定纳税人收入的第一个1000元免征利息税。这会使得( )。

单选题素数是指只含有两个因子的自然数(只能被自身和l整除)。孪生素数，是指两个相差为2的素数。比如，3和5，17和19等。所谓的孪生素数猜想，是由希腊数学家欧几里得提出的，意思是存在无穷对孪生素数。该论题一直未得到证明。近期，美国一位华人讲师的最新研究表明，虽然还无法证明存在无穷多个之差为2的素数对，但存在无穷多个之差小于7000万的素数对。有关方面认为，如果这个结果成立，那么将是数论发展的一项重大突破。 以下哪一项如果为真，最能支持上述有关方面的观点?

单选题在短期生产的边际报酬递减阶段， STC曲线（ ）

单选题亚里士多德的《辨谬篇》记载有这样一则诡辩：“你有一条狗，它是有儿女的，所以它是一个父亲；它是你的，因而它是你的父亲；你打它，就是打你自己的父亲。” 以下哪项犯有与上述诡辩相同的逻辑谬误?

单选题设函数在R上连续，则a=______。

单选题若，则=______．