Male dogs use pheromones in urine to mark their territory, and pheromones are hormones that are thought to stimulate, through smell, sexual reactions in animals. Given these facts, what do male dogs use to mark their territory among the following options:
- smell
 - H 2 O
 - love
 - intuition
 - gourdin
 - tongue
 - sight
 - fur


 

 smell        