The presentation layer is concerned with the (1) and semantics of the information exchanged between two systems. The processes in two systems are usually exchanging information in the form of character(2), numbers, and so on. The information should be changed to bit (3) before being transmitted. Because different computers use different encoding systems, the presentation layer is responsible for(4) between these different encoding methods. The presentation layer at the sender changes the information from its sender-dependent format into a common format. The presentation layer at the receiving machine changes the common format into its(5)-dependent format.
空白（1）处应选择（）
A.frequency
B.syntax
C.dialog
D.format
参考答案：B
解析：
表示层关系到两个系统之间交换的信息的语法和语义。两个系统中的进程通常以字符串、数字等形式交换信息。信息在传输前首先必须被变换成比特流。由于不同的计算机使用了不同的编码系统，所以表示层的任务就是保持这些不同编码方法之间的互操作性。发送方表示层把信息从发送方相关的格式变换为一种通用格式。接收机中的表示层则把通用格式变换为接收方相关的格式。