单选题设，则

单选题设f(x)在[a，b]上二阶可导，且f(x)＞0，下面不等式成立的条件是

单选题设总体Z～N(0，σ2)，Z1，Z2，…，Zn为简单随机样本，则σ2的无偏估计量为

单选题复平面上一等腰三角形的3个顶点按逆时针方向依次为O(原点)、Z1和Z2，，若Z1对应复数，则Z2对应复数z2=______。A．B．C．D．

单选题In the dimly lit cyber-café at Sciences-Po, hot-house of the French elite, no Gauloise smoke fills the air, no dog-eared copies of Sartre lie on the tables. French students are doing what all students do: surfing the web via Google. Now President Jacques Chirac wants to stop this American cultural invasion by setting up a rival French search-engine. The idea was prompted by Google's plan to put online millions of texts from American and British university libraries. If English books are threatening to swamp cyberspace, Mr Chirac will not stand idly by. He asked his culture minister, Renaud Donnedieu de Vabres, and Jean-Noel Jeanneney, head of France's Bibliothèque Nationale, to do the same for French texts--and create a home-grown search-engine to browse them. Why not let Google do the job? Its French version is used for 74% of interuet searches in France. The answer is the vulgar criteria it uses to rank results. "I do not believe", wrote Mr Donnedieu de Vabres in Le Monde, "that the only key to access our culture should be the automatic ranking by popularity, which has been behind Google's success. " This is not the first time Google has met French resistance. A court has upheld a ruling against it, in a lawsuit brought by two firms that claimed its display of rival sponsored links (Google's chief source of revenues) constituted trademark counterfeiting. The French state news agency, Agence France-Presse, has also filed suit against Google for copyright infringement. Googlephobia is spreading. Mr Jeanneney has talked of the "risk of crushing domination by America in defining the view that future generations have of the world. " "I have nothing in particular against Google," he told L' Express, a magazine. "I simply note that this commercial company is the expression of the American system, in which the law of the market is king. " Advertising muscle and consumer demand should not triumph over good taste and cultural sophistication. The flaws in the French plan are obvious. If popularity cannot arbitrate, what will? Mr Jeanneney wants a "committee of experts". He appears to be serious, though the supply of French-speaking experts, or experts speaking any language for that matter, would seem to be insufficient. And if advertising is not to pay, will the taxpayer? The plan mirrors another of Mr Chirac's pet projects : a CNNà la franeaise. Over a year ago, stung by the power of English- speaking television news channels in the Iraq war, Mr Chirac promised to set up a French rival by the end of 2004. The project is bogged down by infighting. France's desire to combat English, on the web or the airwaves, is understandable. Protecting France's tongue from its citizens' inclination to adopt English words is an ancient hobby of the ruling elite. The Académie Francaise was set up in 1635 to that end. Linguists devise translations of cyber-terms, such as arrosage (spam) or bogue (bug). Laws limit the use of English on TV--" Super Nanny" and "Star Academy" are current pests--and impose translations of English slogans in advertising. Treating the invasion of English as a market failure that must be corrected by the state may look clumsy. In France it is just business as usual.

单选题已知xlnx是f(x)的一个原函数，且则a=______．A．B．C．1D．

单选题设f(x)在点x0处不连续，则()。A．f'(x0)必存在B．f'(x0)必不存在C．必存在D．必不存在

单选题已知实数a，b，x，y满足和|x-2|=y-1-b2，则3x+y+3a+b=( )．

单选题设A为3阶可逆矩阵，得A的第2行一3倍加到第1行得B，再将B的第1列的3倍加到第2列得C．记则[]

单选题等差数列{an}的公差不为0，首项a1=1，a2是a1和a5的等此中项，则数列的前10项之和为______ A.90 B.100 C.145 D.190 E.以上答案均不正确

单选题______A.eB.e-1C.eD.e2

单选题对任意实数x，恒有{{U}}{{/U}}．

单选题设A为m×n实矩阵，r(A)=n，则 (A) ATA必合同于n阶单位矩阵． (B) AAT必等价于m阶单位矩阵． (C) ATA必相似于n阶单位矩阵． (D) AAT是m阶单位矩阵．

单选题曲线()

单选题The government requires that a census be taken every five years so that accurate statistics may be ______ . A. composed B. complemented C. completed D. compiled