如果在司钻控制台上操作，但不使用总控制阀，能否控制防喷器的开关？（）

A、防喷器开关速度变快；

B、开关速度不受总控制阀的影响；

C、防喷器开关速度变慢；

D、无法实现防喷器开关操作。

A transport layer protocol has several responsibilities, One is to create a process-to-process (program-to-program) communication; TCP uses port （1） to accomplish this. Anotherresponsibility of a transport layer protocol is to create a（2）and error-control mechanism atthe transport level. TCP uses a sliding（3）protocol to achieve flow control. It uses theacknowledgment packet, time-out, and retransmission to achieve （4） control. The transportlayer is also responsible for providing a connection mechanism for the application program. Theapplication program sends （5）of data to the transport layer. It is the responsibility of thetransport layer at the sending station to make a connection with the receiver.

（5）是（）

A.ports

B.streams

C.packets

D.cells