单项选择题
Charts showing the coast of Mexico are produced by the United States（）.
A.National Geospatial-Intelligence Agency B.Coast Guard C.Naval Observatory D.National Ocean Service
单项选择题 Chart legends which indicate a conspicuous landmark are printed in（）.
单项选择题 Chart legends printed in capital letters show that the associated landmark is（）.
单项选择题 Channel 13 is primarily used for ship to ship communication. Channel 13 is also authorized for（）.
