An oscillator is subjected to a damping force that is proportional to its velocity. A sinusoidal force is applied to it. After a long time: 

A. its amplitude is an increasing function of time 

B. its amplitude is a decreasing function of time 

C. its amplitude is constant 

D. its amplitude is a decreasing function of time only if the damping constant is large 

E. its amplitude increases over some portions of a cycle and decreases over other portions