When a ball is thrown straight up with initial velocity Vo, its position as a function of time is given by

X = Xo + Vo t + 1/2 g t2

This quadratic equation has two roots for 't' for a given value of X.

What does this mean?

A. One root correspond to throwing the ball upward, and the other root corresponds to throwing the ball downward.

B. One root gives the time when the ball reaches a given elevation on the way up, the other gives the time at which the ball passes that point on the way down

C. One of the roots has no physical significance and must be discarded

D. Although there are in principle two root, in fact they always turn out to be equal - i.e. they are not distinct roots