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.
（75）处填（）。
A．correspondent
B．comparable
C．similar
D．analogous
参考答案：C
解析：
参考译文
在数据通信中，数据链路是指在两台数据终端设备之间，由某一协议所控制的那些部分以及互联的数据电路，这两部分合在一起使数据得以传送。所谓“协议”，简单说就是确定完成通信任务的各功能单元行为的一组规则。
数据电路则由一对关联的传输信道组成，用于为双向数据传输提供一种手段。在两台数据交换机之间，数据电路是否可以包括数据电路终接设备(DCE)，这取决于在数据交换机处所用接口的类型。在数据站与数据交换机或数据集中器之间，数据电路包括数据站末端的DCE，并可包括数据交换机或数据集中器处类似于DCE的设备。