单项选择题
How is variation indicated on a small-scale nautical chart?（）
A.Magnetic compass table B.Magnetic meridians C.Isogonic lines D.Variation is not indicated on small-scale nautical charts
单项选择题 Gyrocompass repeaters reproduce the indications of the master gyrocompass. They are（）.
单项选择题 Error may be introduced into a magnetic compass by（）.
单项选择题 Due to GPS roll over of the clock cycle，GPS receivers may give the wrong time and position or may lock up permanently on（）.
