GMAT Critical Reasoning (CR) | Re: Capuchin monkeys in Venezuela often rub a certain type of

Capuchin monkeys in Venezuela often rub a certain type of millepede into their fur. Secretions of these millipedes have been shown to contain two chemicals that are potent mosquito repellents, and mosquitoes carry parasites that debilitate the capuchins. The rubbing behavior is rare except during the rainy season, when mosquito populations are at their peak. Therefore monkeys probably rub millipedes into their fur only because doing so helps protect them against mosquitoes.
Which of the following