Which procedure describes a properly controlled experimental investigation a scientist could have conducted?A. Ten iris plants are planted in an outdoor garden, and they all receive the same amount of sunlight and water each day.B. Five leopard frogs are fed only grub worms, while five toads are fed a mixture of grub worms and fish meal.C. A researcher takes a poll to determine the most popular brand of automotive tire.D. Twenty mice are fed high-protein diets, another 20 mice are fed their usual diet, and their weights are measured after three weeks.
