You are interested in how different air temperatures affect the speed at which gas molecules move. With a classmate, you have planned the following investigation: Choose a very hot day in the classroom.

The students close all of the windows and doors in the classroom and turn off any fans.
The students measure the temperature in the classroom with a thermometer.
One student stands in the corner of the classroom with a stopwatch.
Another student, 10 meters away in the opposite corner of the room, opens a container filled with a safe, but strong-smelling gas.
The student with the stopwatch measures the amount of time before they can smell the gas.
Repeat the steps above on a very cold day in the classroom.
Identify the independent variable in this investigation from the list below:

A. The temperature of the room
B. Amount of time before they smell the gas
C. The distance between the two students in the room
D. Not enough information is provided to identify the independent variable
E. The type of gas in the container