A student stands at the entrance of her school and notes the colors of cars that enter the parking lot. The results are shown in the bar graph below. A histogram titled Cars Entering Parking Lot has car color on the x-axis and frequency on the y-axis. Blue, 7; black, 12; red, 5; white, 8; other, 9.

Which of the following is a true statement regarding the information shown in the bar graph?

Car color is a discrete variable.
Car color is a categorical variable.
Car color is a continuous variable.
Frequency is a discrete variable.