Lily's birthday is _________ spring.[ ]
A. in
B. in the
C. in a
答案：A
低氧性肺血管收缩是指（）
A.肺泡低氧引起的肺小静脉收缩
B.肺泡高二氧化碳引起的肺动脉收缩
C.肺泡高二氧化碳引起的肺静脉收缩
D.肺泡低氧引起的肺小动脉收缩
E.肺泡低氧引起的肺支气管收缩
A transport layer protocol usually has several responsibilities. One is to create a process-to-processcommunication UDP uses（1）numbers to accomplish this. Another responsibility is to provide controlmechanisms at the transport level, UDP does this task at a very minimal level. There is no flow control mechanismand there is no（2）for received packet. UDP, however, does provide error control to some extent. If UDPdetects 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 sendstreams of data to the transport layer. It is the responsibility of the transport layer at （4） station to make theconnection with the receiver chop the stream into transportable units, number them, and send them one by one. Itis the responsibility of the transport layer at the receiving end to wait until all the different units belonging to thesame process have arrived, check and pass those that are （5）free, and deliver them to the receiving process asa stream.
（3）是（）
A.jobs
B.processes
C.programs
D.users
