What did the researchers do after they gave the fish shots? A: They gave all the fish in the fish tank some painkilling shots. B: They put painkilling medicine in the water of both sides of the fish tank. C: They put painkilling medicine in the water of the natural side of the fish tank. D: They put painkilling medicine in the water of the empty side of the fish tank.

What happened after the researchers put painkilling medicine in the water? A: Fish that received the painful shot stayed in the natural section. B: Fish that received the painful shot moved into the empty section. C: All of the fish stayed in the natural section with plants and rocks. D: All of the fish moved into the empty section with painkilling medicine.