The function f(x) = −x^2 − 5x + 50 shows the relationship between the vertical distance of a diver from a pool's surface f(x), in feet, and the horizontal distance x, in feet, of a diver from the diving board. What is a zero of f(x), and what does it represent?

A. x = 5; the diver jumps in the pool at 5 feet per second
B. x = 10; the diver jumps in the pool at 10 feet per second
C. x = 10; the diver hits the water 10 feet horizontally from the board
D. x = 5; the diver hits the water 5 feet away horizontally from the board