The height of a seat on a Ferris wheel can be modeled as H(t)=48 sin (π/20t+ 3π/2) +54 , where t is time in seconds and H(t) is height in feet. How far off the ground is a seat when it is at the top of the Ferris wheel?
A. 54 feet
B. 96 feet
C. 102 feet
D. 108 feet