In data communication, data link is those parts of two data terminal equipments that are controlled by a protocol along with the (71) data circuit, which together enable data (72) . So-called protocol means, in short, a set of rules that determines the behavior of functional units in achieving communication.

Data circuit, however, consists of a pair of (73) transmission channels that provides a means of two-way data transmission. Between data switching exchanges, the data circuit may or may not include data circuit-terminating equipment (DCE), depending on the type of (74) used at the data switching exchange. Between a data station and a data switching exchange or data concentrator, the data circuit includes the DCE at the data station end, and may include equipment (75) to a DCE at the data switching exchange or dam concentrator location.

（74）处填（）。

A．interface

B．port

C．window

D．entrance

在淘宝交易中若买家向卖家反馈收到货与宝贝描述不符，卖家处理正确的是（）。

A、联系买家提供收到货物的照片，核对自己仓库的货物

B、告知买家实物与描述有一定出入是正常的

C、认真比对照片，若确实是我自己的过错，承担运费给买家退换货

D、描述是介绍性的以收到实物为准