单选题已知球体里恰好内接一个正方体，则正方体的体积与球的体积的比是______．A．3:4πB．C．D．E．4π:3

单选题设α，β为四维非零的正交向量，且A=αβT，则A的线性无关的特征向量个数为( )

单选题设A，P均为3阶矩阵，PT为P的转置矩阵，且若P=(α1，α2，α3)，Q=(α1+α2，α2，α3)，则QTAQ为A．B．C．D．

单选题设ξ1=[1，-2，3，2]T，ξ2=[2，0，5，-2]T是线性齐次方程组AX=0的基础解系，则下列向量中是齐次线性方程组AX=0的解向量的是( )．

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