生物上的完美令人不寒而栗，因为那等于同种生物没有变异，进化过程失去动力。我们接受生物的多样化，可是却假定完美是物理和工程科学可欲而又可及的目标。这种观念起源于我们对许多简单问题了解得比较透彻，而“简单”往往意味着对缺陷的忽略。 这段话主要支持了这样一种观点，即( )。

A．完美不可能在科学上实现

B．生物科学比物理和工程科学更深奥

C．缺陷对人类整个技术文明是绝对必须的

D．在物理和工程科学中完美是可欲而又可及的

For each blank, choose the best answer from the four choices and write down on the answer sheet.
(66) 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.
(67) is a professional organization of individuals in multiple professions which focuses on effort on lower-layer protocols.
(68) functions with two layers of protocols. It can connect networks of different speeds and can be adapted to an environment as it expands.
(69) is the popular LAN developed under the direction of the IEEE 802.5.
(70) 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.

A．Ethernet

B．Token Bus

C．Token Ring

D．DQDB