A scientist made an experiment to know the effect of percentage of salinity in water on metabolic rate of clownfish. What is the correct procedure?

a) put 10 clownfish in fresh water at 15 C, and 10 clownfish in salt water at 30 C.
b) put 10 clownfish in fresh water at 15 C, and 10 clownfish in fresh water at 30 C.
c) put 10 clownfish in fresh water at 15 C, and 10 clownfish in salt water at 15 C.
d) put 10 clownfish in fresh water at 30 C, and 10 clownfish in salt water at 15 C