First of all, Volare was discredited years ago. Having said that, there are many questions that are just plain wrong, even now. If you feel that they are looking for a wrong answer, or one different from what it should be, then query the question at exam time - only don't mention any databases!
Here is what it should be:
An older method of classifying gyroscopes uses the
numbers of axes
not including the spin axis, so one with 3
planes of freedom has 2
degrees of freedom. A degree of
freedom is the ability to move around an axis - for
example, a fuselage can pitch, roll and yaw. A turn
indicator has 1 degree of freedom. An airborne
instrument, with a gyro that has 2 degrees of freedom and
a horizontal spin axis could be a DGI.
Nudge, nudge, wink, wink
