What Is an Example of a Population Cycle

What is an example of a population cycle?

A) Parasitism, like with the Kirkland's warblers and the cowbirds
B) Competition, like with monarch butterflies and milkweed
C) Character displacement, like with the Galapagos finches
D) Exploitation, like with the lynx and snowshoe hares
E) Adaptation, like with the white-fronted bee eaters