手术显微镜的基本结构包括（）。
A.双目镜
B.单个大物镜
C.一对棱镜
D.Galilean望远镜或天文望远镜系统
E.以上选项都正确
参考答案：E
请画一风管法兰连接图例。
Changing rescuers while carrying out artificial respiration should be done（）.
A.without losing the rhythm of respiration
B.only with the help of two other people
C.by not stopping the respiration for more than 5 minutes
D.at ten-minute intervals
