As we know that, for a body executing SHM the average kinetic energy is equal to average potential energy over a complete time period i.e. KEav​=PEav​=41​mω2a2 ∴ Total mechanical energy at any time = Sum of kinetic and potential energy =21​mω2a2= constant. where, m = mass of body executing SHM, ω = angular frequency and a = amplitude of SHM. Hence, (c) and (d) are true.