The lowest natural frequency of a five degree-of-freedom system is \(30 \mathrm{rad} / \mathrm{s}\). Select the differential equation which could be the equation for the principal coordinate.

(a) \(\ddot{p}_{1}+\dot{p}_{1}=g_{1}(t)\)

(b) \(\ddot{p}_{1}+30 \dot{p}_{1}=g_{1}(t)\)

(c) \(\ddot{p}_{1}+900 \dot{p}_{1}=g_{1}(t)\)

(d) \(\ddot{p}_{1}=g_{1}(t)\)