单选题In promising to fuse media as diverse as television, telephone communication, video games, music and data transmission, the era of digital convergence goes better than yesterday's celebrated "information superhighway". Yet achieving this single technology is far from straightforward. There are currently three major television broadcast standards, and they are all incompatible with each other. But this is nothing compared to the many technologies supporting the Internet, each with a different bandwidth and physical media. The problems faced in designing platforms and communication systems that will be accepted across the world can appear insuperable. Even once global standards are assured, however, a further obstacle lies in wait. The Internet is plagued by long, erratic response times because it is a pull-technology, driven by patterns of user demands. Push technology, on the other hand, reverses the relationship: servers simply send information to passive users, as in television and radio. But if some form of combination between one-way television flow and interactive Internet is to be the basis of our future media, it is hard to see how it could be operated. Moreover, the problem of fusing Internet with television is also one of defining the services offered. Information, entertainment and relaxation appear at first to be quite different needs. Serious doubts remain over whether consumers will be interested in having to make the sort of mental effort associated with computing while also settling down in front of a sitcom. Besides the issue of consumer habits, infrastructure costs are set to be immense, and will have to be met by national states or the private sector before being passed on to users. Platforms do not necessarily have to be expensive. The mobile phone is a good example of how something that is technologically sophisticated can almost be given away, with its cost recovered through service charges. Users are then coerced through clever marketing to upgrade to newer phones with more features to reinforce their dependence. Whatever the outcome, it is obvious that technology will play an increasing part in our everyday lives. Beyond technology, digital convergence embraces the services, industrial practices and social behavior that form modern society. We have in our hands the technology to construct the most sophisticated machines ever built, but if they are unusable, simply because of their operating instructions, then recent lessons have taught us they will not survive. Whatever we design must be simple, reliable and useful. Perhaps this is where artificial intelligence will come in.

单选题设A为m×n矩阵，且r(A)=m＜n，则下列结论不正确的是{{U}} {{/U}} A. A的m个行向量线性无关 B. A存在m个线性无关的列向量 C. |AAT|≠0 D. |ATA|≠0

单选题行列式第4行元素的余子式之和为()

单选题以下结论，错误的是______A．若0＜P(B)＜1，则A，B相互独立B．若A，B满足P(B|A)=1，则P(A-B)=0C．设A，B，C是三个事件，则(A-B)∪B=A∪BD．若当事件A，B同时发生时，事件C必发生，则P(C)＜P(A)+P(B)-1

单选题A是n阶矩阵，下列命题中错误的是______．

单选题下列极限正确的是A．．B．．C．．D．．

单选题设D是以点A(1，1)，B(-1，1)，C(-1，-1)为顶点的三角形区域，则．

单选题设

单选题设函数F(u，v，w)具有一阶连续偏导数，且方程F(x-y，y-z，z-x)=0确定隐函数z=z(x，y)，则(A)0．(B)1．(C)x．(D)y．

单选题将一枚均匀硬币连续抛n次，以A表示“正面最多出现一次”，以B表示“正面和反面各至少出现一次”，则______A．n=2时，A与B相互独立．B．n=2时，AＢ.C．n=2时，A与B互不相容．D．n=3时，A与B相互独立．

单选题______A．B．C．D．

单选题设A是n阶正定矩阵，B是n阶反对称矩阵，则矩阵A-B 2 是①对称阵，②反对称阵，③可逆阵，④正定阵，四个结论中，正确的个数是______

单选题设A，B为随机事件，且BA考虑下列式子①P(A+B)=P(A)；②P(AB)=P(B)；③P(B-A)=P(B)-P(A)；④P(B|A)=P(B)，其中正确的个数为

单选题设a，b，c为待定常数，则微分方程y"-3y'+2y=3x-2ex的特解具有形式 A.(ax+b)ex． B.(ax+b)xex． C.(ax+b)+cex． D.(ax+b)+cex．