Design a controlled experiment to test the effect of water temperature on goldfish. Be sure to include your hypothesis, independent variable, dependent variable, as well as the experimental and control groups in your experiment.

In this experiment, indepedent variable will be temperature and dependent variable will be the respiratory rate of goldfish. Temperature affects the respiratory rate of goldfish, as it's respiratory rate decreases with decrease in temperature of water, the experiment is as follows:

Take two glass containers filled with water A and B and put one goldfish in each container.Measure the temperature of the water using a thermometer.Count mouth movement of both the fishes in certain time.Now put some ice in container B that will decrease the temperature of water and measure the temperature again.Now count the mouth movement of both the fishes for the same time it was counted earlier.

The result will be that respiratory rate of goldfish decreases with the decrease in temperature in container B in comparison to container A goldfish.

Answer is D: membrane filtration