第一节
听下面5段对话。每段对话后有一道小题,从题中所给的A、B、C三个选项中选出最佳选项,并标在试卷的相应位置。听完每段对话后,你都有10秒钟的时间来回答有关小题和阅读下一小题。每段对话仅读一遍。
听力原文:M: I hear some students in your class visited the Great Wall.
W: You are right.
M: How many students went there?
W: Only half a dozen.
How many students visited the Great Wall?
All the students.
B. Ten students.
C. About six.
政府应当是公共产品和服务的惟一提供者。 ()
A. 正确
B. 错误
Which of the following is true about the woman?
A. She was not aware of the problem.
B. She does not want to sign the contract.
C. She thinks the project is too expensive.
D. She wants Mr. Miller to handle the project.
以下对于数据库的几种关键字的描述中,错误的是(20)。
A. 主关键字一定是候选关键字
B. 候选关键字一定是超关键字
C. 超关键字—定是合成关键字
D. 外部关键字一定是某个关系的候选关键字