Which statement best defines a fair test in a plant growth experiment?

Which statement best defines a fair test in a plant growth experiment?

• A. A fair test changes only one variable at a time; controls ensure no other variables influence results.
• B. A fair test uses different containers and soils to maximize data.
• C. A fair test changes only one variable at a time and uses identical containers, same soil, sunlight, and water.
• D. A fair test relies on subjective judgments of growth.

Answer: (C)