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问题 多项选择题

用重铬酸钾标定硫代硫酸钠标准溶液时，正确的操作有（）

A.应在碱性环境下反应

B.加硫酸酸化

C.终点前加淀粉指示剂

D.滴定温度不应高于20℃

E.加过量碘化钾

答案

参考答案：B, C, D, E

选择题

— Sam, my iPhone is in my bedroom. Could you ____________ it for me?

— No problem.

A．bring

B．get

C．take

D．carry
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单项选择题

Melissa and Love Letter made use of the trust that exists between friends or colleagues. Imagine receiving an (66) from a friend who asks you to open it. This is what happens with Melissa and several other similar email (67) . Upon running, such worms usually proceed to send themselves out to email addresses from the victim’ s address book ,previous emails, web pages (68) .
As administrators seek to block dangerous email attachments through the recognition of well- known (69) , virus writers use other extensions to circumvent such protection. Executable (.exe) files are renamed to . bat and . cnd 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 (70) access to your network.

A．virtual

B．virus

C．worms

D．bacteria
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