单选题已知f(x)在x=0某邻域内连续，且f(0)=0，，则在点x=0处f(x)______。A．不可导B．可导但f'(x)≠0C．取得极大值D．取得极小值

单选题已知，B和C是某两个不同的3阶矩阵，那么a=7是使AB=AC成立的

单选题有一个四位数，它被121除余2，被122除余109，则此数字的各位数字之和为______．

单选题两只一模一样的铁罐里都装有大量的红球和黑球，其中一罐(取名“甲罐”)内的红球数与黑球数之比为2:1，另一罐(取名“乙罐”)内的黑球数与红球数之比为2:1，今任取一罐并从中依次取出50只球，查得其中有30只红球和20只黑球，则该罐为“甲罐”的概率是该罐为“乙罐”的概率的( )倍．

单选题函数y=e x +e -x 的单调增加区间是______

单选题抽签面试时，从8个考题中任取1个题解答，如果8个题中有2个难题、6个容易题，第3名考生抽到难题的概率p=()．

单选题The day was star-crossed: Friday the 13th in the month of October, on the eve of the second looming anniversary of a devastating market crash. "I'm telling you, psychology is really funny. People get crazy in situations like that," said portfolio strategist Elaine Garzarelli. Last week Friday the 13th lived up to its frightful reputation. After drifting lower at a sleepy pace for most of the day, the Dow Jones industrial average abruptly lurched into a hair-raising sky dive in the final hour of trading. The Bush Administration moved swiftly to avert any sense of crisis after the market closed. Declared Treasury Secretary Nicholas Brady: "It's important to recognize that today's stock market decline doesn't signal any fundamental change in the condition of the economy. The economy remains well balanced, and the outlook is for continued moderate growth." But Massachusetts Democrat Edward Markey, who chairs a House subcommittee on telecommunications and finance, vowed to hold hearings this week on the stock market slide. Said he: "This is the second heart attack. My hope is that before we have the inevitable third heart attack, we pay attention to these problems." Experts found no shortage of culprits to blame for the latest shipwreck. A series of downbeat realizations converged on Friday, ranging from signs of a new burst of inflation to sagging corporate profits to troubles in the junk-bond market that has fueled major takeovers. The singular event that shook investors was the faltering of a $6.75 billion labor management buyout of UAL, the parent company of United Airlines, the second largest U. S. carrier. On one point most thoughtful Wall Streeters agreed: the market had reached such dizzying heights that a correction of some sort seemed almost inevitable. Propelled by favorable economic news and a wave of multibillion-dollar takeovers, stocks had soared more than 1,000 points since the 1987 crash. But by last August some Wall streeters were clearly worried. The heaviest blow to the market came Friday afternoon. In a three-paragraph statement, UAL said a labor-management group headed by Chairman Stephen Wolf had failed to get enough financing to acquire United. Several banks had apparently balked at the deal, which was to be partly financed through junk bonds. The take-over group said it would submit a revised bid "in the near term,' but the announcement stunned investors who had come to view the United deal as the latest sure thing in the 1980s buyout binge. Said John Downey, a trader at the Chicago Board Options Exchange: "The airline stocks have looked like attractive takeover targets. But with the United deal in trouble, everyone started to wonder what other deals might not go through./

单选题已知函数y=f(x)在实数集上恒有f"(x)＞0，f"(x)＞0，则曲线y=f(x)的图象______。

单选题设区域D：1≤x2+y2≤22，f是区域D上的连续函数，则等于______A．B．C．D．

单选题设z=z(x，y)是由方程yz+1=0确定的函数，则等于______。A．B．C．D．

单选题已知双曲线的中心在原点且一个焦点为，直线y=x-1与其相交于M，N两点，MN的中点的横坐标为，则该双曲线的方程为()．

单选题设A，B，C均为n阶矩阵，E为n阶单位矩阵，若B=E+AB，C=A+CA，则B-C为

单选题产业结构发展的趋势是______。 A．农业的基础地位被削弱 B．第三产业所占比重不断增大 C．工业比重逐步增大 D．高科技产业占基础地位

单选题设ƒ（x+1）=x（x+1），则ƒ（2）=（　）

单选题向量组α 1 ，α 2 ，…，α m 线性无关的充分必要条件是______.

单选题微分方程的通解为( ) 

单选题已知某厂生产x件产品的成本为要使平均成本最小，所应生产的产品件数为______件．

单选题用五种不同的颜色涂在图9—1中四个区域里，每一区域涂上一种颜色，且相邻区域的颜色必须不同，则共有不同的涂法()．

单选题设y(x)是微分方程y"+(x-1)y"+x2y=ex满足初始条件y(0)=0，y"(0)=1的解，则______.

单选题设f(x)连续，且满足则关于f(x)的极值问题有()