I think it might be a or d i hope i have helped :)
Answer:
The equation for the object's displacement is 
Explanation:
Given:
m = 16 lb
δ = 3 in
The stiffness is:

The angular speed is:

The damping force is:

Where
FD = 20 lb
u = 4 ft/s = 48 in/s
Replacing:

The critical damping is equal:

Like cc>c the system is undamped
The equilibrium expression is:

Uranus is much much larger than Earth, so the distance from the planet's center is much much greater
The answer is Eficiency=T<< Tox100