单项选择题
A single vertical magnet placed underneath the compass in the binnacle is used to compensate for（）.
A.the horizontal component of the permanent magnetism B.deviation caused by the vessel's inclination from the vertical C.induced magnetism in the horizontal soft iron D.induced magnetism in the vertical soft iron
单项选择题 A compass card without north-seeking capability that is used for relative bearings is a(n)（）.
单项选择题 （）is on the panel of DF.
单项选择题 Quadrantal error in a gyrocompass has its GREATEST effect（）.
