单选题设三阶常系数齐次线性微分方程有特解y1=ex，y2=2xex，y3=3e-x，则该微分方程为()

单选题某人射击5枪，命中3枪，3枪中恰有2枪连中的概率为()．

单选题设f(x)在闭区间[0，1]连续，则曲线y=f(x)与直线x=0，x=1和y=0所围成的平面图形的面积等于______。A．B．C．D．不确定

单选题设函数内连续，且，则常数a，b满足

单选题展开式中的常数项是()．A．12B．20C．-12D．-20

单选题下列表中可成为离散型随机变量的分布列的是A．B．C．D．

单选题"It is an evil influence on the youth of our country. " A politician condemning video gaming? Actually, a clergyman denouncing rock and roll 50 years ago. But the sentiment could just as easily have been voiced by Hillary Clinton in the past few weeks, as she blamed video games for "a silent epidemic of media desensitisation" and "stealing the innocence of our children". The gaming furore centers on "Grand Theft Auto: San Andreas", a popular and notoriously violent cops and robbers game that turned out to contain hidden sex scenes that could be unlocked using a patch downloaded from the internet. The resulting outcry (mostly from Democratic politicians playing to the centre) caused the game's rating in America to be changed from "mature", which means you have to be 17 to buy it, to "adults only", which means you have to be 18, but also means that big retailers such as Wal-Mart will not stock it. As a result the game has been banned in Australia; and, this autumn, America's Federal Trade Commission will investigate the complaints. That will give gaming's opponents an opportunity to vent their wrath on the industry. Skepticism of new media is a tradition with deep roots, going back at least as far as Socrates' objections to written texts, outlined in Plato's Phaedrus. Socrates worried that relying on written texts, rather than the oral tradition, would "create forgetfulness in the learners' souls, because they will not use their memories; they will trust to the external written characters and not remember of themselves." (He also objected that a written version of a speech was no substitute for the ability to interrogate the speaker, since, when questioned, the text "always gives one unvarying answer". His objection, in short, was that books were not interactive. Perhaps Socrates would have thought more highly of video games. ) Novels were once considered too low-brow for university literature courses, but eventually the disapproving professors retired. Waltz music and dancing were condemned in the 19th century; all that twirling was thought to be "intoxicating" and "depraved", and the music was outlawed in some places. Today it is hard to imagine what the fuss was about. And rock and roll was thought to encourage violence, promiscuity and Satanism ; but today even grannies buy Coldplay albums.

单选题下列结论正确的是

单选题设集合M={1，2，3，4，5}，N={2，4.6}，则M∩N=（　）

单选题坚持四项基本原则和坚持改革开放统一于______。 A．社会主义革命中 B．建设中国特色社会主义的实践中 C．坚持四项基本原则中 D．改革开放中

单选题已知f’(cos x)=sin x，则f(cos x)= ( )

单选题设向量组α 1 ，α 2 ，α 3 为方程组AX=0的一个基础解系，下列向量组中也是方程组AX=0的基础解系的是______．

单选题某种同样的商品装成一箱，每个商品的重量都超过1千克，并且是1千克的整数倍，去掉箱子重量后净重210千克，拿出若干个商品后，净重183千克，则每个商品的重量为______千克．

单选题设随机变量X和Y都服从标准正态分布，则______。

单选题 若在区间内，函数的一阶导数>0二阶导数,则函数在区间内 A、单调减少，曲线上凹 B、单调减少，曲线下凹 C、单调增加，曲线上凹 D、单调增加，曲线下凹。

单选题一水池装有甲、乙、丙三个进水管．单独开放甲管，45小时可以注满全池；单独开放乙管，60小时可注满；单独开放丙管，90小时可注满．若三管一齐开放，注满水池需( )小时．

单选题下列结论中不正确的是( )．

单选题设f(x)是连续函数，F(x)是f(x)的原函数，则下列各项中正确的是( )。

单选题函数f(x)在点x=x 0 处连续是f(x)在x 0 处可导的______

单选题如题18图所示，g(x)的图形是直线段OB，f(x)的图形是折线段OAC，u(x)=f[g(x)]，则u′(4)=()．