The Height of the Falling Sheet of Paper, in Feet $s ( t ) = - 1.5 t + 9$

Multiple Choice

The height of the falling sheet of paper, in feet from the ground, is given by $s ( t ) = - 1.5 t + 9$ after t seconds.
When will the sheet of paper reach the ground

A) after 9 seconds
B) after 7.5 seconds
C) after 15 seconds
D) after 6 seconds
E) after 3 seconds