单项选择题
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
单项选择题 Carbon dioxide as a fire fighting agent has which advantage over other agents?（）
单项选择题 Camphor oil is classified as a（）.
单项选择题 By regulation，you MUST keep a record of the use of your radiotelephone for a minimum of（）.
