Answer
The flight time of ball C is the longest, then ball B, and finally ball A.
Work Step by Step
The ball is uniform, and is being launched with a constant initial velocity, so the only factor affecting flight time is height of the ball; the higher the ball goes, the longer it stays in the air for. The optimal angle for the greatest range of a flight is 45$^{\circ}$, we can safely infer that the middle of the graph is 45$^{\circ}$ because it has the longest range. Ball C is launched at an angle greater than 45$^{\circ}$, and A is launched at an angle below 45 $^{\circ}$. A higher launch angle means greater height that the projectile hits. Possessing the greatest launch angle, ball C has the greatest flight time.
