单选题x=0是函数的______

单选题关于x的不等式(0＜a＜1)的解集为()．

单选题Science is a dominant theme in our culture. Since it touches almost every facet of our life, educated people need at least some acquaintance with its structure and operation. They should also have an understanding of the subculture in which scientists live and the kinds of people they are. An understanding of general characteristics of science as well as specific scientific concepts is easier to attain if one knows something about the things that excite and frustrate the scientist. This book is written for the intelligent student or lay person whose acquaintance with science is superficial, for the person who has been presented with science as a musty storehouse of dried facts, for the person who sees the chief objective of science as the production of gadgets, and for the person who views the scientists as some sort of magician. The book can be used to supplement a course in any science, to accompany any course that attempts to give an understanding of the modern work, or--independently of any course --simply to provide a better understanding of science. We hope this book will lead readers to a broader perspective on scientific attitudes and a more realistic view of what science is, who scientists are, and what they do. It will give them an awareness and understanding of the relationship between science and our culture and an appreciation of the roles science may play in our culture. In addition, readers may learn to appreciate the relationship between scientific views and some of the values and philosophies that are pervasive in our culture. We have tried to present in this book an accurate and up-to-date picture of the scientific community and the people who populate it. That population has in recent years come to comprise more and more women. This increasing role of women in the scientific subculture is not a unique incident but, rather, part of the trend evident in all segments of society as more women enter traditionally male-dominated fields and make significant contributions. In discussing these changes and contribution, however, we are faced with a language that is implicitly sexist, one that uses male nouns or pronouns in referring to unspecified individuals. To offset this built-in bias, we have adopted the policy of using plural nouns and pronouns whenever possible and, when absolutely necessary, alternating he and she. This policy is far from being ideal, but it is at least an acknowledgment of the inadequacy of our language in treating half of the human race equally. We have also tried to make the book entertaining as well as informative. Our approach is usually informal. We feel, as do many other scientists, that we shouldn't take ourselves too seriously. As the reader may observe, we see science as a delightful pastime rather than as a grim and dreary way to earn a living.

单选题A是n阶矩阵，且A3=0，则______。 A．A不可逆，E-A也不可逆 B．A可逆，E+A也可逆 C．A2-A+E与A2+A+E均可逆 D．A不可逆，且A2必为0

单选题如下图所示，圆内接一个等腰直角三角形，则圆面积与该三角形的面积比值为______．A．B．1C．D．πE．

单选题关于x的一元二次方程x2-x+a(1-a)=0有两个不相等的正根，则实数a的取值范围是______．A．0＜a＜1B．C．D．E．

单选题如果圆(x-a) 2 +(y-b) 2 =1的圆心在第三象限，那么直线ax+by-1=0一定不经过______

单选题已知反常积分和均收敛，则p的取值范围是______A．p＞2．B．p＜2．C．p＞0．D．0＜P＜2．

单选题已知方程x=aex(a＞0)有两个实根，则A．．B．．C．a＞e．D．a＜e．

单选题设随机变量X1，X2，…，Xn(n＞1)独立同分布，且其方差为σ＞0，令随机变量，则

单选题______．

单选题设，在x=0处二阶可导，则常数a，b，c分别是

单选题{{U}}{{/U}}A.0B.1C.eD.-∞

单选题北魏孝文帝下诏，官员在朝议时，三十岁以上者可使用鲜卑语，三十岁以下者应当“从正音(说汉话)”，否则“降爵黜官”。这一措施的实施（　　）