题目内容

下列关于数据库主键的叙述中,不正确的是( )。

A. 主键只允许数字类型的值
B. 主键不允许出现NULL值
C. 主键不允许出现重复值
D. 若不能保证任何单字段都含唯一值,可以将两个或更多的字段指定为主键

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The belief ______ no one is infallible is well founded.

A. which
B. whether
C. how
D. that

73()

A. extensive
B. entire
C. overall
D. enormous

Which of the following statements is TRUE, according to the author()

A. Everyone has a right to hold his own opinion.
B. Free expression of opinions often leads to confusion.
C. Most people tend to be careless in forming their opinions.
D. Casual use of the word "opinion" often brings about quarrels.

可信计算机安全评估准则中,级别最高的是( )。

A类
B. D类
C. B3类
D. C2类

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