题目内容

A．I live in Shanghai.B．I am from Beijing.C．I came yesterday.D．No, thank you.

A. I live in Shanghai.
B. I am from Beijing.
C. I came yesterday.
D. No, thank you.

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第(55)-(56)题基于以下描述：关系模式R(A, B, C, D, E)，根据语义有如下函数依赖集：F=｛A→C，BC→D，CD→A，AB→E} 。
下列属性组中哪个(些)是关系R的候选码？
Ⅰ(A,B)
Ⅱ(A,D)
Ⅲ(B,C)
Ⅳ(C,D)
Ⅴ(B,D)

A. 仅Ⅲ
B. 仅Ⅰ和Ⅲ
C. 仅Ⅰ、Ⅱ和Ⅳ
D. 仅Ⅱ、Ⅲ和Ⅴ

设关系R, S和T如下，关系T是关系R和S执行了哪种操作的结果？

第(32)-(34)题基于“学生一选课一课程”数据库中的三个关系：
S(S#，SNAME，SEX, AGE，DEPARTMENT)主码是S#
C(C#，CNAME, TEACHER)主码是C#
SC(S#, C#, GRADE)主码是(S#，C#)
为了便于识别，当外键与相应的主键属于不同关系时，往往给它们以相同的名字。
下列叙述中，哪个是不正确的？

A. S#是关系S的主键，也是关系SC的外键
B. C#是关系C的主键，也是关系SC的外键
C. 向任何一个关系插入元组时，必须保证关系主码值的唯一性
D. 可以任意删除每个关系中的元组

Section B
Directions: This section is to test your ability to understand short dialogues. There are 5 recorded dialogues in it. After each dialogue, there is a recorded question. The dialogues and questions will be spoken two times. When you hear a question, you should decide on the correct answer from the 4 choices marked A, B, C and D.
(6)

A long trip.
B. An street accident.
C. A difficult course.
D. An easy task.