The acceleration due to Earth's gravity is customarily considered to be -9.8 m/s² for algebra problems, so the value in equations C and D is appropriate to the problem dimensions (m/s). (The equation for ballistic motion uses (1/2)*g = -4.9 m/s².)
Equation C has the initial height of the ball as 45 m, with no vertical velocity. Equation D has the vertical velocity as 45 m/s.
The appropriate choice is ...
D. -4.9t^2+45t = 0
