题目内容
关系代数是关系操纵语言的一种传统表示方式，它以集合代数为基础，它的运算对象和运算结果均为（）。
查看答案
搜索结果不匹配？点我反馈
更多问题
Twenty years ago, kids in school had never even heard of the Internet. Now, I’ll bet you can’t find a single person in your school who hasn’t at least heard of it. (76) In fact, many of us use it on a regular basis and even have access to it from our homes! The “net” in Internet really stands for network. A network is two or more computers connected together so that information can be shared, or sent from one computer to another. The Internet is a vast resource for all types of information. (77) You may enjoy using it to do research for a school project, downloading your favorite songs or communicating with friends and family. Information is accessed through web pages that companies, organizations and individuals create and post. It’s kind of like a giant bulletin board (布告牌) that the whole world uses! (78) But since anyone can put anything on the Internet, you also have to be careful and use your best judgment and a little common sense.Just because you read something on a piece of paper someone sticks on a bulletin board doesn’t mean it’s good information, or even correct, for that matter. So you have to be sure that whoever posted the information knows what they’re talking about, especially if you’re doing research! But what if you’re just emailing people You still have to be very careful. (79) If you’ve never met the person that you’re communicating with online, you could be on dangerous ground! You should never give out any personal information to someone you don’t know, not even your name! And just like you can’t believe the information on every website out there, you can’t rely on what strangers you “meet” on the Internet tell you either. (80) Just like you could make up things about yourself to tell someone, someone else could do the same to you!76.77.78.79.80. In fact, many of us use it on a regular basis and even have access to it from our homes!
毛细胞白血病与下列疾病相符合的细胞化学染色（）
Passage OneQuestions 61 to 65 are based on the following passage:Testing has replaced teaching in most public schools. My own children’s school week is focused on pretests, drills, tests, and retests. I believe that my daughter Erica, who gets excellent marks, has never read a chapter of any of her school textbooks all the way through. And teachers are often heard to state proudly and openly that they teach to the state test.Teaching to the test is a curious phenomenon. Instead of deciding what skills students ought to learn, helping students learn them, and then using some sensible methods of assessment (评估) to discover whether students have mastered the skills, teachers are encouraged to reverse the process. First one looks at a test. Then one draws the skills needed not to master, say, reading, but to do well on the test. Finally, the test skills are taught.The ability to read or write or calculate might imply the ability to do reasonably well on standard tests. However, neither reading nor writing develops simply through being taught to take tests. We must be careful to avoid mistaking preparation for a test of a skill with the acquisition of that skill. Too many discussions of basic skills make this fundamental confusion because people are test obsessed rather than concerned with the nature and quality of what is taught.Recently many schools have faced with what could be called the crisis of comprehension or, in simple terms, the phenomenon of students with grammar skills still being unable to understand what they read. These students are good at test taking, but they have little or no experience reading or thinking, and talking about what they read. They are taught to be so concerned with grade that they have no time or ease of mind to think about meaning, and reread things if necessary. What are students encouraged to do nowadays at school
甲公司承租乙公司一座楼房绎营，为预防经营风险，甲公司将此楼房投保500万元，保险公司经过核实认为甲公司拥有对该楼房的承租权，所以具有保险利益，同意承保，甲公司交付了一年的保险金，9个月后甲公司结束租赁，将楼房退还给乙公司。在保险期的第10个月该楼房发生了火灾，损失300万元。甲公司根据保险合同的约定向保险公司主张赔偿，并提出保险合同、该楼房受损失的证明等资料。保险公司经过调查后拒绝承担赔偿责任。试分析： 保险公司拒绝赔偿的法律依据何在？
微信支付 
支付宝支付