For each blank，choose the best answer from the four choices and write down on the answer sheet.

（ ）is a six bytes OSI layer 2 address which is burned into every networking device that provides its unique identity for point to point communication.

（ ）is a professional organization of individuals in multiple professions which focuses on effort on lower-layer protocols.

（ ）functions with two layers of protocols.It Can connect networks of different speeds and can be adapted to an environment as it expands.

（ ）is the popular LAN developed under the direction of the IEEE 802.5.

（ ）is the popular backbone technology for transmitting information at high speed with a high level of fault tolerance which is developed under the direction of ANSI.