In the OSI architecture, what directly serves the Application Layer is（）
A. Presentation Layer
B. Conversation Layer
C. Transport Layer
D. Network Layer
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In the OSI reference model, which of the basic unit of transmission is frame（）
A. Data Link Layer
B. Physical Layer
C. Network Layer
D. Transport Layer
The semantics of the three elements of network protocol stipulate（）
A. What should communication parties “say” when communicating
B. “How to say” in communication
C. Structure or format of data and control information
D. Execution sequence of communication events
IP protocol is located in（）of the TCP/IP architecture
A. Interconnection Network Layer
B. Application Layer
C. Transport Layer
D. Network access Layer
The syntax of the three elements of network protocol stipulates that（）
A. “How to say” in communication
B. Explanation of contents to be expressed by both parties in communication
C. What should communication parties “say” when communicating
D. Execution sequence of communication events
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