一般资料：求助者，男性，29 岁，未婚，博士，公司高级管理人员。案例介绍：求助者的父

A transport layer protocol usually has several responsibilities．One is to create a process-to-process communication；UDP uses (1) numbers to accomplish this．Another responsibility is to provide control mechanisms at the transport level．UDP does this task at a very minimal level．There is no flow control mechanism and there is no(2) for received packet．UDP, however, does provide error control to some extent．If UDP detects an error in the received packet，it will silently drop it． The transport layer also provides a connection mechanism for the processes．The (3) must be able to send streams of data to the transport layer．It is the responsibility of the transport layer at (4) station to make the connection with the receiver, chop the stream into transportable units，number them，and send them one by one．It is the responsibility of the transport layer at the receiving end to wait until all the different units belonging to the same process have arrived，check and pass those that are (5) free, and deliver them to the receiving process as a stream．

（1）处应填（）。

A．hop

B．port

C．route

D．packet

关于心内膜弹力纤维增生症说法正确的是（）

A.可并发脑栓塞

B.多数于l岁以内发病

C.主要应用洋地黄控制心力衰竭

D.以充血性心力衰竭为主要表现

E.常并发支气管炎

钻遇油、气、水层时，钻井液当量密度低于（）就会发生井喷。

A、地层压力

B、地层压力系数

C、地层温度

D、地层压力温度

一般普通建筑室内消火栓系统最不利消火栓处充实水柱不得小于（）。

A、7m

B、10m

C、15m

D、20m

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