For a harmonically excited single degree of freedom viscous damped system which one of the following is correct?
(a) Inertia force leads damping force by 900 while damping force leads spring force by 900
(b) Spring force leads damping force by 900 while damping force leads inertia force by 900
(c) Spring force and damping force are in phase and damping force leads them by 900
(d) Spring force and inertia force are in phase and damping force leads them by 900