PLEASE HELP Question: A marine biologist is testing the hypothesis that cold water promotes the growth of corals. Which of the following study designs may yield the most conclusive results?

A.) Two study sites with stable differing water temperatures, similar water nutrient profiles, and similar coral communities growing at different depths

B.) Two study sites with fluctuating water temperatures, similar coral communities growing at similar depths, with similar water nutrient profiles

C.) Two study sites with the same temperature profile, different coral communities growing at different depths, with different water nutrient profiles

D.) Two study sites with stable differing water temperatures, similar coral communities growing at similar depths, with similar water nutrient profiles