前置胎盘时出现 * * 流血，下列哪项正确：

A．常发生在妊娠中期

B．常伴有下腹部疼痛

C． * * 出血量与贫血程度不成比例

D．妊娠足月出现 * * 出血应考虑为部分性前置胎盘

E．妊娠28周出现 * * 出血应考虑为完全性前置胎盘

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．The MAC address

B．The IP address

C．The subnet address

D．The virtual address