Channel 13 is primarily used for ship to ship communication. Channel 13 is also authorized for（）.

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?（）

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（）.

A.Grade A flammable liquid
B.Grade C flammable liquid
C.Grade D combustible liquid
D.Grade E combustible liquid

单项选择题By regulation，you MUST keep a record of the use of your radiotelephone for a minimum of（）.

A.six months
B.one year
C.two years
D.thirty months

单项选择题By law，a user of marijuana shall be subject to（）.

A.loss of pay during the period of such use
B.reprimand by the US Coast Guard
C.revocation of license or certificate
D.termination of employment