单项选择题
Chronometer error may be found by（）.
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
单项选择题 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（）.
单项选择题 Chart legends printed in capital letters show that the associated landmark is（）.
