The governor is said to be stable when
(a) For each speed within the working range there is only one radius of rotation for the governor ball
(b) The equilibrium speed is constant for all radii rotation of the balls within working range
(c) There is a slightest increase in speed the governor balls will fly to this maximum radius
(d) The governor admits either maximum or minimum amount of energy to the engine and will not admit an amount of energy between these two extremes