Gustavo throws an object straight up with a speed of 20 meters per second. Because of gravity, of course, the object will soon fall back to ground. The equation that describes its speed is
s(t) = -9.8t + 20
Based on the equation above, which of the following is the independent variable?
A. The time
B. The speed of the object
C. The height of the object
D. The pull of gravity