单选题一批救灾物资分别随16列货车从甲站紧急调到600公里以外的乙站，每列车的平均速度都为125公里/小时．若两列相邻的货车在运行中的间隔不得小于25公里，则这批物资全部到达乙站最少需要的小时数为( )． A．7.4 B．7.8 C．8 D．8.2 E．8.4

单选题已知α=(1，-3，2)T，β=(0，1，-1)T，矩阵A=2βαT+7E，则矩阵A的最小特征值的特征向量是 (A) α．(B) β． (C) α+β． (D) α-β．

单选题设A为m×n阶矩阵，B为n×m阶矩阵，且m＞n，令r(AB)=r，则______．

单选题直三棱柱的每个侧面的面积为5，底面积是10，全面积是（　）

单选题下列四个函数不能做随机变量X的分布函数的是______A．B．C．D．

单选题设函数y=y(x)由参数方程，确定，则曲线y=y(x)在x=3处的法线与x轴交点的横坐标是______．A．B．C．-8ln2+3D．8ln2+3

单选题设函数f(x)在区间(-1，1)内二次可导，已知f(0)=0，f'(0)=1，且f"(x)＜0当x∈(-1，1)时成立，则

单选题（　）

单选题设直线nx+(n+1)y=1(n为正整数)与两坐标轴围成的三角形面积Sn(n=1，2，…，2009)，则S1+S2+…+S2009=()．

单选题二重积分的积分区域D可以表示为____

单选题（　　）

单选题The teacher gave the students extra work because she was ______ by all the noise and talking in the classroom. A. interrupted B. degenerated C. terminated D. exasperated

单选题若E(XY)=E(X)E(Y)，则______．

单选题长途汽车从A站出发，匀速行驶，1 h后突然发生故障，车速降低了40%，到B站终点延误达3 h，若汽车能多跑50 km后，才发生故障，坚持行驶到B站能少延误1 h20 min，那么A、B两地相距( )k m．

单选题若f(x)=-f(-x)，在(0，+∞)内f'(x)＞0，f"(x)＞0，则f(x)在(-∞，0)内______．

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 (A) E． (B) -E． (C) A． (D) -A．

单选题For me, scientific knowledge is divided into mathematical sciences, natural sciences or sciences dealing with the natural world (physical and biological sciences), and sciences dealing with mankind (psychology, sociology, all the sciences of cultural achievements, every kind of historical knowledge). Apart from these sciences is philosophy, about which we will talk later. In the first place, all this is pure or theoretical knowledge, sought only for the purpose of understanding, in order to fulfill the need to understand that is intrinsic and con-substantial to man. What distinguishes man from animals is that he knows and needs to know. If man did not know that the world existed, and that the world was of a certain kind, that he was in the world and that he himself was of a certain kind, he wouldn't be man. The technical aspects or applications of knowledge are equally necessary for man and are of the greatest importance, because they also contribute to defining him as man and permit him to pursue a life increasingly more truly human. But even while enjoying the results of technical progress, man must defend the primacy and autonomy of pure knowledge. Knowledge sought directly for its practical applications will have immediate and foreseeable success, but not the kind of important result whose revolutionary scope is for the most part unforeseen, except by the imagination of the Utopians. Let me recall a well-known example. If the Greek mathematicians had not applied themselves to the investigation of conic section zealously and without the least suspicion that it might someday be useful, it would not have been possible centuries later to navigate far from shore. The first men to study the nature of electricity could not imagine that their experiments, carried on because o mere intellectual curiosity, would eventually lead to modern electrical technology, without which we can scarcely conceive o contemporary life. Pure knowledge is valuable for its own sake, because the human spirit cannot resign itself to ignorance. But, in addition, it is the foundation for practical results that would not have been reached if this knowledge had not been sought disinterestedly.

单选题设函数f(x)在|x|＜δ内有定义且|f(x)|≤x 2 ，则f(x)在x=0处______．

单选题已知abc＜0，a+b+c=0，则______．

单选题设，当x→0时，与f(x)等价的无穷小量是()．