Charts showing the coast of Mexico are produced by the United States（）.

单项选择题Chart legends which indicate a conspicuous landmark are printed in（）.

A.underlined letters
B.capital letters
C.italics
D.boldface print

单项选择题Chart legends printed in capital letters show that the associated landmark is（）.

A.inconspicuous 
B.conspicuous
C.a government facility or station
D.a radio transmitter

单项选择题Channel 13 is primarily used for ship to ship communication. Channel 13 is also authorized for（）.

A.coast to aircraft operational communications
B.aircraft to ship operational communications
C.lock & bridge communications
D.aircraft to ship navigational communications

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