Jordana drew the function below. Which statement correctly explains whether or not her function is linear?
On a coordinate plane, a parabola opens up.
A. It is linear because it has a constant rate of change.
B. It is linear because it does not have a constant rate of change.
C. It is not linear because it has a constant rate of change.
D. It is not linear because it does not have a constant rate of change.