设关系T是关系R和S的关系运算结果，且T、R、S的元组个数分别为k、m、n，则k、m、n三者之间的关系是（）

>> 成人高等教育 / 数据库原理与应用

成人高等教育 / 数据库原理与应用

A、
k<( m + n)
B、
k≤( m + n)
C、
k<(m×n)
D、
k≤(m×n)

积分

数据库原理与应用

参考答案：

点击查看答案

佳题速递：

题型描述: 阅读理解How men first learnt to invent words is unknown; in other words, the origin of language is a mystery. All we really know is that men, unlike animals, somehow invented cer?tain sounds to express thought and feelings, actions and things, so that they could communi?cate with each other; and that later they agreed upon certain signs, called letters, which could be combined to present those sounds, and which could be written down. Those sounds, whether spoken or written in letters, we call words.The power of words, then, lies in their associations—the things they bring up before our minds. Words become filled with meaning for us by experience; and the longer we live, the more certain words recall to us the glad and sad events of our past; and the more we read and learn, the more the number of words that mean something increases.Great writers are those who not only have great thoughts but also express these thoughts in words which appeal powerfully to our minds and emotions. This charming and telling use of words is what we call literary style. Above all, the real poet is a master of words. He can convey his meaning in words which sing like music and which by their position and associa?tion can move men to tears. We should therefore learn to choose our words carefully and use them accurately, or they will make our speech silly and vulgar.1、 The origin of language is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . A. a question difficult to answer B. a legend handed down from the past C. a matter that is hidden or secret D. a problem not yet solved 2、 What is true about words? A. They can not be written down. B. They are simply sounds. C. They are mysterious. D. They are used to express feelings only. 3、 The real power of words lies in their _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . A. representative function B. characteristics C. properties D. peculiarity 4、 By "association", the author means _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . A. a joining of ideas in the mind B. a special quality C. an appearance which is puzzling D. a strange feature 5、 Which of the following statements about the real poet is NOT true? A. His style is always charming. B. He is no more than a master of words. C. He can move men to tears. D. He can convey his ideas in words which sing like music.统考英语B

10[单选题] 设有定义：float a=2,b=4,h=3;,以下C语言表达式与代数式计算结果不相符的是 A.(a b)*h/2 B.(1/2)*(a b)*h C.(a b)*h*1/2 D.h/2*(a b)面向对象程序设计

幼儿园班级管理状况的调查内容一般包括以下几个方面：班风班纪、----------、财产管理、养成教育等正确答案是：安全卫生、教育教学幼儿园班级管理

9[计算题] 简述合成氨在国民经济中的重要作用化工基础

[填空题] 重被花是具有_____和_____的花药用植物学

47、在PowerPoint2010浏览视图下，按Ctrl+M键，完成的操作是_______。 A.移动幻灯片 B.复制幻灯片 C.删除幻灯片 D.插入一张新幻灯片计算机统考