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问题 单项选择题

在数据库表中，要求指定字段或表达式不出现重复值，应该建立的索引是

A．惟一索引

B．惟一索引和候选索引

C．惟一索引和主索引

D．主索引和候选索引

答案

参考答案：D

选择题

27. We haven’t settled the question of ____ it is necessary for him to study abroad.

A．if

B．where

C．whether

D．That
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填空题

根据句意，用括号内所给单词的适当形式填空

1. This pair of boots looks very ______(时尚的).

2. Make sure that you write down all the ______ (游客) names on the list.

3. She has to be taken to hospital because she has taken lots of ______(药).

4. His sudden ______(死) made me very sad.

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