A biologist studying a desert ecosystem observes that the population of a lizard species increases following particularly hot, dry period that causes a snake population to decline. What could the biologist hypthesize about the roles of these two species?

A) The lizard preys on the snake

B) The lizard is a parasite of the snake

C) The snake and lizard use the same limiting resource

D) The snake is a keystone species in the ecosystem.