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（）.
单项选择题 Changing rescuers while carrying out artificial respiration should be done（）.
单项选择题 Carbon dioxide as a fire fighting agent has which advantage over other agents?（）
