单选题下列结论不正确的是(A)若函数f(x，y)在有界闭区域D上可积，则至少存在一点(ξ，η)∈D，使得，其中S为D的面积．(B)若函数f(x，y)在有界闭区域D上连续，且f(x，y)在D上的平均值为零，则至少存在一点(ξ，η)∈D，使得f(ξ，η)=0．(C)设函数f(x，y)在区域D：(x-x0)2+(y-y0)2≤ρ2上连续，则(D)若函数f(x，y)在区域D上连续，且满足f(-x，-y)=-f(x，y)，则，其中D：|x|≤a，|y|≤b．

单选题关于x的方程k2x2+(2k-1)x+1=0有实数根，则下列说法正确的是( )。

单选题设α1=(1，4，3，-1)T，α2=(2，t，-1，-1)T，α3=(-2，3，1，t+1)T，则______。 A.对任意的t，α1，α2，α3线性无关 B.仅当t=-3时，α1，α2，α3线性无关 C.当t=0时，α1，α2，α3线性相关 D.仅t≠0且t≠-3时，α1，α2，α3线性无关

单选题设f'(x)为连续函数，则等于()．

单选题已知则sinx=[]．A．B．C．D．

单选题如图6—3，已知△ABC为等腰直角三角形，∠A=90°，△BDC为等边三角形，则可确定△BDC的面积为(1)△ABC的周长为(2)△ABC的面积为2

单选题问N为多少? (1)N只有2和3两个质因子 (2)N的因子个数为12。 (A) 条件(1)充分，但条件(2)不充分． (B) 条件(2)充分，但条件(1)不充分． (C) 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分． (D) 条件(1)充分，条件(2)也充分． (E) 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．

单选题设复数z满足，则|1+z|=()．

单选题 For most of us, work is the central, dominating fact of life. We spend more than half our conscious hours at work, preparing for work, traveling to and from work. What we do there largely determines our standard of living and to a considerable extent the status we are accorded by our fellow citizens as well. It is sometimes said that because leisure has become more important the indignities and injustices of work can be pushed into a comer, that because most work is pretty intolerable, the people who do it should compensate for its boredom, frustration and humiliations by concentrating their hopes on the other parts of their lives. I reject that as a counsel of despair. For the foreseeable future the material and psychological rewards which work can provide, and the conditions in which work is done, will continue to play a vital part in determining the satisfaction that life can offer. Yet only a small minority can control the pace at which they work or the conditions in which their work is done; only for a small minority does work offer scope for creativity, imagination, or initiative. Inequality at work and in work is still one of the cruelest and most glaring forms of inequality in our society. We cannot hope to solve the more obvious problems of industrial life, many of which arise directly or indirectly from the frustrations created by inequality at work, unless we tackle it head-on. Still less can we hope to create a decent and humane society. The most glaring inequality is that between managers and the rest. For most managers, work is an opportunity and a challenge. Their jobs engage their interest and allow them to develop their abilities. They are constantly learning; they are able to exercise responsibility; they have a considerable degree of control over their own and others' working lives. Most important of all, they have opportunity to initiate. By contrast, for most manual workers, and for a growing number of white-collar workers, work is a boring, dull, even painful experience. They spend all their working lives in conditions which would be regarded as intolerable--for themselves--by those who take the decisions which let such conditions continue. The majority have little control over their work; it provides them with no opportunity for personal development. Often production is so designed that workers are simply part of the technology. In offices, many jobs are so routine that workers justifiably feel themselves to be mere cogs in the bureaucratic machine. As a direct consequence of their work experience, many workers feel alienated from their work and their firm, whether it is in public or in private ownership.

单选题从5个不同的黑球和2个不同的白球中，任选3个球放入3个不同的盒子中，每盒1球，其中至多有1个白球的不同放法共有______种．

单选题已知F1、F2是椭圆(a＞b＞0)的两焦点，B为椭圆在y轴上的顶点，∠F1BF2=120°，则椭圆的离心率e=()．

单选题设f(x)在x0处可导，g(x)在x0处不连续，则f(x)g(x)在x0处 (A) 必不连续． (B) 可能连续必不可导． (C) 可能可导但导数必不连续． (D) 可能存在任意阶导数．

单选题[2013年1月]已知二次函数f(x)=ax 2 +bx+c，则方程f(x)=0有两个不同实根。 (1)a+c=0； (2)a+b+c=0。