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问题 选择题

下列有关免疫系统的叙述，正确的是[ ]

A．吞噬细胞、T细胞、B细胞等都属于免疫淋巴细胞

B．抗体、淋巴因子、血红蛋白等都属于免疫活性物质

C．免疫系统只能对付外来病原体，不能抑制肿瘤的发生

D．免疫系统具有防卫、监控和清除等功能

答案

答案：D

单项选择题

When the system upon which a transport entity is running fails and subsequently restarts, the (1) information of all active connections is lost. The affected connections become half-open, as the side that did not fail does not yet realize the problem.

The still active side of a half-open connection can close the connection using a (2) timer. This timer measures the time the transport machine will continue to await an (3) of a transmitted segment after the segment has been retransmitted the maximum number of times. When the timer (4) , the transport entity assumes that either the other transport entity or the intervening network has failed. As a result, the timer closes the connection, and signals an abnormal close to the TS user.

In the event that a transport entity fails and quickly restarts, half-open connections can be terminated more quickly by the use of the RST segment. The failed side returns an RST i to every segment i that it receives. When the RST i reaches the other side, it must be checked for validity based on the (5) number i, as the RST could be in response to an old segment. If the reset is valid, the transport entity performs an abnormal termination.

4（）

A.stops 

B.restarts 

C.expires 

D.abandons
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单项选择题

“三化三铁”工作实行等级评定、（）管理。

A.动态

B.静态

C.集中

D.统一
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