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问题 选择题

能影响水的电离平衡，并使溶液中的c(H+)>c(OH-)的操作是[ ]

A．向水中投入一小块金属钠

B．将水加热煮沸

C．向水中通入二氧化碳气体

D．向水中加食盐晶体

答案

答案：C

单项选择题

Melissa and LoveLetter made use of the trust that exists between friends or colleagues. Imagine receiving an (6) from a friend who asks you to open it. This is what happens with Melissa and several other similar email (7) . Upon running, such worms usually proceed to send themselves out to email addresses from the victim’s address book, previous emails, web pages (8) .

As administrators seek to block dangerous email attachments through the recognition of well-known (9) , virus writers use other extensions to circumvent such protection. Executable (.exe) files are renamed to .bat and .cmd plus a whole list of other extensions and will still run and successfully infect target users.Frequently, hackers try to penetrate networks by sending an attachment that looks like a flash movie, which, while displaying some cute animation, simultaneously runs commands in the background to steal your passwords and give the (10) access to your network.

7（）

A.virtual

B.virus

C.worms

D.bacteria
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选择题

在学习中，为了完成一项学习任务，几位同学可以组成一个学习小组。大家共同探讨，密切配合，完成学习任务；同时也可以与其他小组展开竞争，提高效率。这样的学习小组[     ]

A．不是一个具有竞争力的团队

B．既存在合作，又存在竞争

C．不能实现共同的目标

D．不利于整个班级凝聚力的形成

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