题目内容
设有高校选课系统，需要对学校的系信息、教师信息、课程信息、学生信息、学生选课信息进行管理。已知系(DEPT)信息包括系编号(DeptNO)、系名称(DeptName)；教师(1'eacher)信息包括教师号(1'NO)、教师名(TName)；课程(Course)信息包括课程号(CNO)、课程名(CName)、课程学分(Credit)；学生(Student)信息包括学号(SNO)、学生姓名(SName)、学生性别(Sex)。
选课系统的管理规则如下：
i．一个系可聘用多名教师，一名教师只受聘于一个系；
ii．一个系可有多名学生，一名学生只属于一个系；
iii．一名教师可讲授多门课程，一门课程可由多名教师讲授；
iv．一名学生可选修多门课程，一门课程可被多个学生选修；
v．学生选修完课程后，可获得相应课程的成绩。
请针对以上描述，完成下列设计内容：
①构建选课系统的E—R图。(要求图中的实体集名用试卷中给出的英文名，联系名用联系所关联的实体集名的首字母，字母间用“一”或“一”连接，大小写不限)
②根据所构建的E—R图，设计满足3NF的关系模式，并标出每个关系模式的主码和外码。
(要求关系模式名同实体集名或联系名，属性名用试卷中给出的英文名，大小写不限)
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In which two ways are the lines distinguished from each other？
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Section A
Directions: In this section, you will hear 8 short conversations and 2 long conversations. At the end of each conversation, one or more questions will be asked about what was said. Both the conversation and the questions will be spoken only once. After each question there will be a pause. During the pause, you must read the four choices marked A, B, C and D, and decide which is the best answer.
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