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问题 单项选择题

作为对PKI的最基本要求，PKI必须具备的性能是（）

A.支持多政策

B.透明性和易用性

C.互操作性

D.支持多平台

答案

参考答案：B

实验题

小刚家准备建一栋新房，爸爸买了一堆材料相同的石子，小刚选取一块石子在实验室测它的密度．

（1）他将托盘天平放在水平桌面上，把游码移到标尺左端的“0”刻度线处，观察指针的指示情况如（图1）所示，此时应进行的操作是                      ；天平横梁调平衡后，在称物体的质量时，他在天平右盘中加、减砝码后，指针的指示情况如（图2）所示，这时他应进行的操作是                        ．

（2）小刚按图甲所示的方法测石子的质量，请指出操作中的两个错误：

①                   ；

②                   ．

（3）纠正错误后继续实验，当盘中所加砝码和游码位置如图乙所示时天平平衡，则此石子的质量为          g．在量筒内装有一定量的水，该石子放入前．在量筒内装有一定量的水，该石子放入前、后的情况如图丙所示，则石子的体积是          cm3，此石子的密度是            kg/m3．
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Questions


·Read the following passage and choose the best word for each space.
Do you want to send an e-mail message to the White House
Good luck.
In the past, (26) President Bush — or at least those assigned to read his mail — what was (27) your mind it was necessary only to sit down at a personal computer connected to the lnternet and (28) a note to president@ whitehouse.gov.
But this week, Tom Matzzie, an online organizer with the A.F.L.-C.I.O., discovered that (29) with the White House had become a bit more (30) . When Mr. Matzzie sent an e-mail protesting (31) a Bush administration policy, the message was bounced back With an automated reply, saying he had to send it again in a new way.
Under a system (32) on the White House Website (33) the first time last week, those who want to send a message to President Bush must now (34) as many as nine Web pages and (35) a detailed form that starts by asking whether the message sender supports White House policy (36) differs with it.
The white House says the new e-mail system is an effort to be more responsive (37) the public and offer the administration "real time" access (38) citizen comments.
Completing a message to the president also requires (39) a subject from the provided list, then entering a full name, organization, address and e-mail address. (40) the message is sent, the writer must wait for an automated response (41) his message, (42) whether the addressee intended to send the message. The message is delivered to the White House only after the person using that e-mail address (43) it.
"Over (44) , it’s a very cumbersome process," said Jakob Nielsen, an authority on Web design. "It’s probably designed deliberately to (45) on their e-mail.\

A. andB. or C. notD. nor
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