In the OSI reference model, the main function of the Physical Layer is（）
A. Transparently transmitting bit streams
B. Access control and management of data link
C. Transferring data frames between physical entities
D. Transferring data frames between physical entities
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Which is at the bottom of the OSI reference model（）
A. Physical Layer
B. Application Layer
C. Network Layer
D. Transport Layer
In the OSI reference model, the first bottom-up level to provide end-to-end services is（）
A. Transport layer
B. Network Layer
C. Data Link Layer
D. Application Layer
A system that uses various means of communication to organically connect geographically dispersed autonomous computers to realize mutual communication and share hardware, software and data resources i
A. Computer network
B. Terminal time sharing system
C. Distributed computer system
D. Multi machine system
ARPANET is the predecessor of the Internet. It is a（）
A. Packet switching network
B. Circuit switching network
C. Message Switching Network
D. Mixed Switching Network
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