单项选择题
The reaction of a gyrocompass to an applied force is known as（）.
A.precession B.earth rate C.gyroscopic inertia D.gravity effect
单项选择题 The quadrantal spheres are used to（）.
单项选择题 The principal purpose of magnetic compass adjustment is to（）.
单项选择题 The permanent magnetism of a vessel may change in strength due to（）.
