单项选择题
A.radio time signal B.comparison with a timepiece of known error C.applying the prevailing chronometer rate to previous readings D.All of the above
Charts showing the coast of Mexico are produced by the ...
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
Chart legends which indicate a conspicuous landmark are...
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
Chart legends printed in capital letters show that the ...
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
