A scientist found a correlation between the oxygen level in
a pond and the water temperature. As the water
temperature increased, the oxygen level decreased.
To find out whether the change in the water temperature caused the oxygen
level to change, what could the scientist do?
A. Measure water temperature at various depths in the pond to find
out whether it changes.
B. Compare oxygen levels with carbon dioxide levels in water at
various temperatures.
C. Perform a controlled experiment by increasing and decreasing
water temperature and measuring changes in oxygen levels.
D. Add more oxygen to the water and take measurements to
determine whether the temperature changes.