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问题 填空题

某金属质量为m，体积为V，若该金属质量为2m，则密度为______．

答案

某金属质量为m，体积为V，则金属的密度ρ=

m
V
，

密度是物质的固有属性，与物质的质量无关，若该金属质量为2m，则密度仍为

m
V
．

故答案为：

m
V
．

单项选择题

异步电动机在正常运转时，转子磁场在空间的转速为（）。

A、转子转速

B、同步转速

C、转差率与转子转速的乘积

D、转差率与同步转速的乘积
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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 (26) from a friend who asks you to open it. This is what happens with Melissa and several other similar email (27) . Upon running, such worms usually proceed to send themselves out to email addresses from the victim’s address book, previous emails, web pages (28) .

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

As administrators seek to block dangerous email attachments through the recognition of well-known (29) , 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 (30) access to your network.
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