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问题 单项选择题

数据库管理系统通常提供授权功能来控制不同用户访问数据的权限，这主要是为了实现数据库的

A．可靠性

B．一致性

C．完整性

D．安全性

答案

参考答案：D

解析：解析：为了实现数据库的安全性，数据库管理系统通常提供授权功能来控制不同用户访问数据的权限。

判断题

购物券是一种有价证券。( )
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单项选择题

The greatest chance for the existence of extraterrestrial life is on a planet beyond our solar system. The Milky Way galaxy alone contains 100 billion other suns, many of which could be accompanied by planets similar enough to Earth to make them suitable abodes of life.
The statement above assumes which of the following

A．Living creatures on another planet would probably have the same appearance as those on Earth.

B．Life cannot exist on other planets in our solar system.

C．If the appropriate physical conditions exist, life is an in evitable consequence.

D．More than one of the suns in the galaxy is accompanied by an Earth-like planet.

E．(E) It is likely that life on another planet would require conditions similar to those on Earth.
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