单项选择题
Gyrocompass repeaters reproduce the indications of the master gyrocompass. They are（）.
A.accurate only in the Polar regions B.accurate electronic servomechanisms C.hand operated D.accurate only if the vessel is underway
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（）.
单项选择题 Deviation which is maximum on intercardinal compass headings may be removed by the（）.
