单选题装台机器需要甲，乙，丙三种部件各一件，现库中存有这三种部件共270件，分别用甲，乙，丙库存件数的装配若干机器，那么原来存有甲种部件()．

单选题设，若，则n的最小值为()。A．7B．8C．9D．10

单选题设常数k≠0，则为______

单选题若双曲线经过点，且它的两条渐近线的方程是，则双曲线方程是()。

单选题It is no longer just dirty blue-collar jobs in manufacturing that are being sucked offshore but also white-collar service jobs, which used to be considered safe from foreign competition. Telecoms charges have tumbled, allowing workers in far-flung locations to be connected cheaply to customers in the developed world. This has made it possible to offshore services that were once non-tradable. Morgan Stanley's Mr. Roach has been drawing attention to the fact that the "global labour arbitrage" is moving rapidly to the better kinds of jobs. It is no longer just basic data processing and call centres that are being outsourced to low-wage countries, but also software programming, medical diagnostics, engineering design, law, accounting, finance and business consulting. These can now be delivered electronically from anywhere in the world, exposing skilled white-collar workers to greater competition. The standard retort to such arguments is that outsourcing abroad is too small to matter much. So far fewer than lm American service-sector jobs have been lost to off-shoring. Forrester Research forecasts that by 2015 a total of 3.4m jobs in services will have moved abroad, but that is tiny compared with the 30m jobs destroyed and created in America every year. The trouble is that such studies allow only for the sorts of jobs that are already being off-shored, when in reality the proportion of jobs that can be moved will rise as IT advances and education improves in emerging economies. Alan Blinder, an economist at Princeton University, believes that most economists are underestimating the disruptive effects of off-shoring, and that in future two to three times as many service jobs will be susceptible to off-shoring as in manufacturing. This would imply that at least 30% of all jobs might be at risk. In practice the number of jobs off-shored to China or India is likely to remain fairly modest. Even so, the mere threat that they could be shifted will depress wages. Moreover, says Mr. Blinder, education offers no protection. Highly skilled accountants, radiologists or computer programmers now have to compete with electronically delivered competition from abroad, whereas humble taxi drivers, janitors and crane operators remain safe from off-shoring. This may help to explain why the real median wage of American graduates has fallen by 6% since 9000, a bigger decline than in average wages. In the 1980s and early 1990s, the pay gap between low-paid, low-skilled workers and high-paid, high-skilled Workers widened significantly. But since then, according to a study by David Autor, Lawrence Katz and Melissa Kearney, in America, Britain and Germany workers at the bottom as well as at the top have done better than those in the middle-income group. Office cleaning cannot be done by workers in India. It is the easily standardised skilled jobs in the middle, such as accounting, that are now being squeezed hardest. A study by Bradford Jensen and Lori Kletzer, at the Institute for International Economics in Washington D. C., confirms that workers in tradable services that are exposed to foreign competition tend to be more skilled than workers in non-tradable services and tradable manufacturing industries.

单选题一只船顺流而行的航速为30km/h，已知顺水航行3h和逆水航行5h的航程相等，则此船顺水漂流1h的航程为( )km．

单选题Some would consider that an infringement of good manners whereas others would not. A. an example B. a violation C. a problem D. an indication

单选题设z=x 3 -3x-y，则它在点(1，0)处

单选题设x1，x2是方程x2-(a2+2)x+a=0(1≤a≤3)的两个实根，则的最小值为()．

单选题一个圆柱底面直径和高都为8，一个圆锥底面直径和高都为4，则圆锥和圆柱的体积比为{{U}} {{/U}}． A.1:2 B.1:24 C.1:2 D.1:4

单选题一个等差数列的前12项的和为354，前12项中偶数项的和与奇数项的和之比为 32:27，则公差d＝( )．

单选题The guest {{U}}turned upside down{{/U}} his glass as a signal that he would drink no more. A. conversed B. inversed C. traversed D. reversed

单选题在等差数列{an}中，a1=1，公差d≠0，a2，a3，a6成等比数列，则d=（　）

单选题设f(x)除以(x-1)2的余式是x+2，除以(x-2)2的余式是3x+4，则f(x)除以(x-1)(x-2)2的余式是{{U}} {{/U}}． A. 4x2-19x+12 B. -4x2+19x-12 C. -4x2-19x-12 D. 4x2+19x-12

单选题设a，b，c为实数，且ab，则（　）

单选题下列定积分等于零的是()

单选题在等比数列an中，a1＞1，且前n项和Sn满足，那么a1的取值范围是()。A．(1,+∞)B．(1,4)C．(1,2)D．(1,)

单选题已知α1=(-1，1，a4)T，α2=(-2，1，5，a)T，α3(a，2，10，1)T是四阶方阵A的属于三个不同特征值的特征向量，则a的取值为____．

单选题趣味运动会中，6个人共同参加争夺三个项目的冠军，每项设一个冠军，则冠军归属的可能结果有______．

单选题设直线方程为，平面方程为2x+8y-6z+1=0，则该直线与该平面的位置关系是()。A．平行B．垂直C．直线在平面内D．相交但不垂直