Q:Fact 1: Male dogs use pheromones in urine to mark their territory. Fact 2: Pheromones are hormones that are thought to stimulate, through smell, sexual reactions in animals. Given the two facts above, answer the question "What do male dogs use to mark their territory?" with the following options: - smell - H 2 O - love - intuition - gourdin - tongue - sight - fur
A:
smell