A student is planning an investigation of the effect of population size on an ecosystem. She plans to use a five-gallon fish tank with ten goldfish for her investigation. How should the student perform her investigation? A. She should limit the amount of food given and observe the results. B. She should add a predator fish to the tank and observe the results C. She should continue to add more goldfish to the tank and observe the results D. She should change the temperature of the water in the tank and observe the results.​