Look at the five paths in the figure again: five balls thrown at $20\ \text{m/s}$, at $15^\circ$, $30^\circ$, $45^\circ$, $60^\circ$ and $75^\circ$. Which ball stays in the air the longest?

Fig. 1: A graph of height against horizontal distance with the paths of five balls thrown at 20 m/s, at 15, 30, 45, 60 and 75 degrees.