(51) 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.

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

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

(54) is the popular LAN developed under the direction of the IEEE802.5.

(55) 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.

（52）是（）

A.ISO

B.ANSI

C.CCIT

D.IEEE

关于汗液的叙述，错误的是

A．是高渗液体

B．固体成分主要含Na+、K+、Cl一和尿素

C．交感神经兴奋时分泌增加

D．大量出汗可导致高渗性脱水

E．阿托品可使汗液分泌减少