Afarmer had an accident and spilled a chemical into his pond. several days later, he notices many dead frogs around the pond. that summer, the number of gnats around the pond was higher than ever. this is because a) the chemical is good for the gnats. b) the frogs are a limiting factor for the gnats. c) the gnats are a limiting factor for the frogs. d) the chemical is a limiting factor for the gnats.