If a projectile is launched vertically upward from the ground with an initial velocity of 45 ft per sec, neglecting air resistance, its height s (in feet) above the ground t seconds after projection is given by

s = -16t² + 45t.

Which equation should be used to determine the height of the projectile after 2 sec?

A. s = 2(-16t² + 45t) 

B. s = -16(2)² + 45(2)

C. 2 = -16t² + 45t 

D. 2 = -16t²