单选题 The presentation layer is concerned with the ______ and semantics of the information exchanged between two systems. The processes in two systems are usually exchanginginformation in the form of character ______, numbers, and so on. The information should bechanged to bit ______ before being transmitted. Because different encoding systems, thepresentation layer is responsible for ______ between these different encoding methods. Thepresentation layer at the sender changes the information from its sender-dependent format into acommon format. The presentation layer at the receiving machine changes the common format intoits ______ dependent format.

【正确答案】 B

【答案解析】[解析] 表示层关注两个系统之间信息交换的语法和语义。两个系统中通常是以字符串和数字等形式交换信息。传输前必须将信息转换成比特流。因为在不同的编码系统中，表示层负责这些不同的编码方式之间的互操作性。在发送端的表示层把信息的发送者相关格式转换为通用格式。在接收机器的表示层把通用格式转换成接收器相关格式。