Which of the following would be a reason for a species to undergo cyclic population changes?

The keystone species in its ecosystem is removed.

The vegetation it eats increases and then decreases repeatedly with changing seasons.

Its predator is preyed upon by a new species introduced to the ecosystem.

Climate change alters the prevalence of parasites that affect the species.

Question

Which of the following would be a reason for a species to undergo cyclic population changes? 

The keystone species in its ecosystem is removed.

The vegetation it eats increases and then decreases repeatedly with changing seasons.

Its predator is preyed upon by a new species introduced to the ecosystem.

Climate change alters the prevalence of parasites that affect the species.

geometry_hater · Answer

But in this case its cyclic population wich means theres alot of food for the animals to eat and then the population explodes and vice versa.

so its The vegetation it eats increases and then decreases repeatedly with changing seasons.

anonymous · Answer

I agree that the correct answer is B [the vegetation...]. However, all the other answers could result in a decrease of the population of the specie (but it wouldn't be cyclic).