A student observed a difference in the activity level of fish at a pet store. the fish in the aquarium near the window are swimming around more quickly than the fish in an aquarium placed in the back of the store. The student forms a hypothesis about the effect of sunlight on fish activity levels and arranged to conduct and experiment. Which variable could be an independent variable in the student's experiment? 1.) type of fish sold
2.) speed of swimming fishes
3.) amount of time fish were active
4.) temperature of water in fish tank