The correct statement based on the principles of energy conservation in a roller coaster scenario is:
Both potential and kinetic energy change, but total energy does not change.
In a roller coaster, as it moves along the track, the potential energy (due to height) and kinetic energy (due to motion) will change at different points (A, B, C, D), but the total mechanical energy (the sum of potential and kinetic energy) remains constant if we neglect friction and air resistance.