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问题 选择题

若a＞0，b＞0，且a≠1，则logab＞0是（a-1）（b-1）＞0的（　　）

A．充分不必要条件

B．必要不充分条件

C．充要条件

D．既不充分又不必要条件

答案

因为a＞0，b＞0，a≠1，

则若logab＞0成立，当a＞1时，有b＞1；当0＜a＜1，有0＜b＜1，则“（a-1）（b-1）＞0”成立；

若“（a-1）（b-1）＜0”，有a＞1且b＞1或0＜a＜1且0＜b＜1则“logab＞0”

故“logab＞0”是“（a-1）（b-1）＞0”的充要条件

故选C

单项选择题

Unless negotiations begin soon, the cease-fire will be violated by one of the two sides to the dispute. Negotiations will be held only if other countries have pressured the two sides to negotiate; an agreement will emerge only if other countries continue such pressure throughout the negotiations. But no negotiations will be held until international troops enforcing the cease-fire have demonstrated their ability to counter any aggression from either side, thus suppressing a major incentive for the two sides to resume fighting.
If the statements above are true, and if negotiations between the two sides do begin soon, at the time those negotiations begin each of the following must also be true EXCEPT:

A．The cease-fire has not been violated by either of the two sides.

B．International troops enforcing the cease-fire have demonstrated that they can counter aggression from either of the two sides.

C．A major incentive for the two sides to resume hostilities has been suppressed.

D．Other countries have exerted pressure on the two sides to the dispute.

E．(E) The negotiations’ reaching an agreement depends in part on the actions of other countries.
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单项选择题

将域名转换成IP地址是由(1)协议来完成的，将IP地址转换成MAC地址是由(2)协议来完成的。

1（）

A．DNS

B．ARP

C．DHCP

D．RARP
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