First of all, the root is [tex] 5 [/tex], since
[tex] -5^2-5\cdot 5 + 50 = -25-25+50=0 [/tex]
Then, since the [tex] x [/tex] represents the horizontal distance, and [tex] f(x) [/tex] the height, we can read [tex] f(5)=0 [/tex] as "the height is zero when the diver is [tex] 5 [/tex] feet away from the board.
So, the answer is D.