动物传染病的主要发展阶段为（）A．潜伏期、前驱期、明显期（发病期）和转归期 B．潜伏

2009年以来，全国文化部门和综合执法机构深入开展整治互联网和手机媒体淫秽色情及低俗信息等专项行动，进一步加大对淫秽、色情及低俗网络游戏的打击整治力度。这样做，体现了对未成年人的    [ ]

A．家庭保护      

B．学校保护      

C．社会保护       

D．司法保护

A transport layer protocol usually has several responsibilities．One is to create a process-to-process communication；UDP uses (71) numbers to accomplish this．Another responsibility is to providecontrol mechanisms at the transport level．UDP does this task at a very minimal level．There is no flowcontrol mechanism and there is no (72) for received packet．UDP, however,does provide errorcontrol 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 (73) must be able to send streams of data to the transport layer．It is the responsibility of the transport layer at (74) station to make the connection with the receiver,chop the stream into transportable units，numberthem，and send them one by one．It is the responsibility of the transport layer at the receiving end to waituntil all the different units belonging to the same process have arrived，check and pass those that are (75) flee，and deliver them to the receiving process as a stream．

A．call

B．state

C．cost

D．error

质押式债券回购交易的实质内容是：（）以持有的债券作抵押，获得一定期限的资金使用权。期满后则需归还借贷资金，并按约定支付一定的利息。

A．逆回购方

B．正回购方

C．融资者

D．融券者

以下情况中，采暖管道可不必保温的是( )。

A．管道敷设在地沟、技术夹层、闷顶或管道井内
B．管道内输送热媒必须保证一定参数
C．不通行地沟内仅供冬季采暖用的凝结水管，余热不利用，且无冻结危险
D．管道通过不采暖房间

发电机不允许在未充氢气和定子线圈未通水的情况下投入励磁升压。