Correct Answer – C
(c) In resonant vibrations of a body , the frequency of external force applied on the body is equal to its natural frequency . If on increasing and decreasing the frequency of external force from the natural frequency by a factor, the amplitude of vibrations reduces very much. In this case , sharp resonance will take place.
But if it reduces by a small factor, then flat resonance will take place. The sharp and flat resonance will depend on damping present in the body execting resonant vibrations. Less the damping , greater will be sharpness.