The graph shows the water level , in centimeters, in a tank minutes after a pump starts filling it. The graph starts at a low water level and curves upwards, becoming progressively steeper as increases. Which of the following statements best describes the rate at which the water level is changing?
The water level is increasing at a constant rate.
The water level is increasing at an increasing rate.
The water level is increasing at a decreasing rate.
The water level is decreasing.
