Which of the following is NOT used as a rodenticide?

Methoxychlor is a synthetic organochlorine compound primarily used as an insecticide, particularly against mosquito populations, and it does not function as a rodenticide. This distinguishes it from the other options listed, which are specifically designed or utilized to target rodent populations.

Bromadiolone, warfarin, and cholecalciferol are all compounds that can be employed as rodenticides. Bromadiolone is an anticoagulant that causes internal bleeding in rodents; warfarin functions similarly by disrupting the blood-clotting process; and cholecalciferol, or vitamin D3, can lead to severe hypercalcemia and subsequent death in rodents.

Thus, identifying methoxychlor as the only choice that is not used as a rodenticide is accurate based on its specific pest control application.