单项选择题
Before a magnetic compass is adjusted certain correctors must be checked to ensure that they are free of permanent magnetism. These correctors are the（）.
A.fore-and-aft and athwartships magnets B.dip needle and heeling magnet C.heeling magnet and Flinders bar D.Flinders bar and quadrantal spheres
单项选择题 Based on your 2209 fix，which would be a warning that you are being set down on Block Island Sound South Entrance Obstruction Lighted BIS Buoy? （）
单项选择题 Based on a DR，at approximately 1817 you would expect to（）.
单项选择题 At the master gyrocompass，the compass card is attached to the（）.
