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问题 选择题

离子方程式CO32－ + 2H+ = H2O + CO2↑中的CO32－代表的物质可以是（   ）

A．CaCO3

B．NaHCO3

C．Na2CO3

D．BaCO3

答案

答案：C

单项选择题

“新经济政策”规定，中小企业和国家暂时无力兴办的企业，允许本国和外国资本家经营。这表明( )。

A．苏俄开始着眼于解决经济困难

B．苏俄充分利用外资发展民族企业

C．苏俄开始利用市场和商品货币关系发展生产以向社会主义过渡

D．苏俄决定实行改革开放
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单项选择题

Melissa and LoveLetter made use of the trust that exists between friends or colleagues. Imagine receiving an (46) from a friend who asks you to open it. This is what happens with Melissa and several other similar E-mail (47) . Upon running, such worms usually proceed to send themselves out to email addresses from the victim’s address book, previous emails, web pages (48) .

A. cracker B. user C. customer D. client

As administrators seek to block dangerous email attachments through the recognition of well-known (49) , 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 (50) access to your network.
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