What is a positive effect that predators have on a prey population? a. they eliminate the prey population in order to maintain competition over resources such as food and water. b. prey are able to increase their populations and use of food, shelter, and water when predators are on the hunt. c. predators maintain an unchanged prey population to increase the use of food, water, and shelter. d. they keep the prey population low so they will be less likely to deplete resources such as food, water, and shelter.