For an underdamped harmonic oscillator, resonance ______.
(A) occurs when excitation frequency is greater than the undamped natural frequency
(B) occurs when excitation frequency is less than the undamped natural frequency
(C) occurs when excitation frequency is equal to the undamped natural frequency
(D) never occurs
(A) occurs when excitation frequency is greater than the undamped natural frequency
(B) occurs when excitation frequency is less than the undamped natural frequency
(C) occurs when excitation frequency is equal to the undamped natural frequency
(D) never occurs