The graph below models the value of a $20,000 car t years after it was purchased. Value of Car

A graph titled Value of Car has years on the x-axis and Dollars on the y-axis. A line curves down and goes through points (0, 20,000), (4, 10,000), and (14, 2,000).

Which statement best describes why the value of the car is a function of the number of years since it was purchased?
Each car value, y, is associated with exactly one time, t.
Each time, t, is associated with exactly one car value, y.
The rate at which the car decreases in value is not constant.
There is no time, t, at which the value of the car is 0.