下列词语中有4个错别字，找出来抄写在横线上，然后改正。

融汇贯通　山清水秀　失之交臂　死心踏地　万籁俱寂

可见一般　纹丝不动　无缘无故　再接再厉　身体力形

错别字_______________________________________

订正_________________________________________

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

The application program sends （） of data to the transport layer.

A．ports

B．streams

C． packets

D．cells