We need to see the predator relationships that exist in the system but also the competition for various food sources. The fact that eagles decrease, means that their direct prey, snakes will increase in numbers; similarly, the grass will increase for a while; but rabbit were competing with gnats for the grass. Now that rabbits are gone, the gnats will proliferate. Now, knowing that, we can eliminate answer choices b, c, d, so we are technically done. To verify e), notice now that the snakes that are preying on frogs will increase in numbers; thus the frogs will decrease.
