WAEC - Physics (2001 - No. 8)
The amplitude of the motion of a body performing simple harmonic motion decreases with time because
friction force dissipate the energy of motion
the frequency of oscillation varies with time
the period of oscillation varies with time
energy is supplied by some external agency
Uitleg
The amplitude of the motion of a body performing simple harmonic motion (SHM) decreases over time primarily due to energy loss, often caused by friction or other resistive forces. Therefore OPTION A is correct.