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问题 单项选择题

Access中，设置为主键的字段

A．不能设置索引

B．可设置为“有(有重复)”索引

C．系统自动设置索引

D．可设置为“无”索引

答案

参考答案：C

解析： 本题考查的是主键的概念及其操作。在Access系统中，设置为主键的字段由系统自动设置索引。

改错题

此题要求改正所给短文的错误。 如有错误 则按下列情况改正：

多一个词：把多余的词用斜线（\）划掉，

缺一个词：在缺词处加一个漏字符号（∧）， 并写出该加的词。

该行错一个词：在错的词下划一横线， 在横线下写出改正后的词。

注意：没有错的不要改。

I am good at all the subjects，and always ready help others.At school I get along well with my classmates.Therefore，I have a problem that troubles myself all the time.It's the relationship among my deskmate and me.He is a hard­working student，who keeps school rule well.But he's a person with few words.What's more，he got angry easily.I don't know what to deal with him.Maybe it's why we've seldom sat down to exchange our feelings or thoughts.I value our friendship.I hope we can know more about with each other and understand each other better.I do hope we will be close to each other than before.
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选择题

下列反应中，属于加成反应的是 [ ]

A．CH4+Cl2CH3Cl+HCl

B．CH2=CH2+HClCH3CH2Cl

C．2CH3CH2OH+O22CH3CHO +2H2O

D．

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