如图1-30（原图1-42）所示，物体G用两根绳子悬挂，开始时绳OA水平，现将两绳同时顺时针转过90°，且保持两绳之间的夹角a不变（a>90°），物体保持静止状态，在旋转过程中，设绳OA的拉力为T₁，绳OB的拉力为T₂，则（    ）。

A．T₁先减小后增大

B．T₁先增大后减小

C．T₂逐渐减小

D．T₂最终变为零

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. namesB. cookies C. software D. extensions

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.