Indeed. If you still are in doubt if your first answer was (fully) correct, then try look at the equation and think about what you have to do to the mass (but with constant radius) to increase the surface gravity, and likewise what you have to do to the radius (but with constant mass) for the same to happen again. You may also think about if it is possible to achieve the higher level of surface gravity if both mass and radius had increased or if both had decreased at the same time. After all that the answer to the original question would then simply be a list of all the combinations of increase, constant and decrease of mass and radius that allow a higher surface acceleration to be achieved.