In a study to explore the effects of ambient temperature on concentration levels, participants are placed in rooms set at either 18°C or 25°C. Their performance on a series of mental math tests is then measured. What is the independent variable in this study?

• A. The type of math tests
• B. The performance on the math tests
• C. The ambient temperature of the rooms
• D. The time spent in the rooms

Answer: (C)