关于机械能,下列说法正确的是() A.物体做竖直面内的圆周运动,机械能一定守恒

题型:选择题

问题:

关于机械能,下列说法正确的是(    )

A.物体做竖直面内的圆周运动,机械能一定守恒

B.物体做匀速直线运动,机械能一定守恒

C.物体必须在只受重力的情况下,机械能才守恒

D.只有重力对物体做功时,物体的机械能一定守恒

考点:机械能守恒定律
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项目目标评估一般采用的方法为( )。

A.逻辑框架法

B.层次分析法

C.多目标评价法

D.矩阵分析法

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A型行为类型的人容易好发()

A.原发性高血压

B.冠心病

C.哮喘

D.癌症

E.消化性溃疡

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会计数据基本的输出形式是( )。

A.查询和打印

B.上传

C.统计

D.显示

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副根管多见于

A.切牙
B.尖牙
C.前磨牙
D.磨牙
E.额外牙

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Melissa and LoveLetter made use of the trust that exists between friends or colleagues. Imagine receiving an (56) from a friend who asks you to open it. This is what happens with Melissa and several other similar Email (57) . Upon running, such worms usually proceed to send themselves out to Email addresses from the victim’s address book, previous Emails, Web pages (58)
As administrators seek to block dangerous Email attachments through the recognition of well-known (59) , 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 (60) access to your network.

A.cracker

B.user

C.customer

D.client

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