The correct answer is letter D. Water. The resources that is considered natural, biotic and exhaustible is D. Water. Water is in itself part of nature that is why it is natural. It is biotic. Most especially, water is considered to last in the future. It most probably present in the coming days.
B. the frogs are a limiting factor for the gnats the frogs limit the reproduction of the gnats, and therefore with less frogs the gnat population can increase
