The correct answer is B) G is above M. Unstable equilibrium exists at small angles of inclination when the metacenter (M) is below the center of gravity (G). In this case, any small disturbance will cause the vessel to continue heeling over, instead of returning to an upright position. This is because the righting moment (the force trying to right the vessel) acts to increase the heel, rather than decrease it. The other options are incorrect because they do not describe the condition for unstable equilibrium. A) G off the centerline and D) B off the centerline do not directly affect the stability, while C) B above G would actually result in stable equilibrium.