单项选择题
Carbon dioxide as a fire fighting agent has which advantage over other agents?（）
A.It causes minimal damage B.It is safer for personnel C.It is cheaper D.It is most effective on a per unit basis
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（）.
单项选择题 By law，a user of marijuana shall be subject to（）.
