Male dogs use pheromones in urine to mark their territory, and pheromones are natural aphrodisiacs. Given these facts, what do male dogs use in their urine to mark their territory among the following options:
- feces
 - layers of fat
 - natural aphrodisiacs
 - food
 - Something coming from a gland
 - Chemical energy
 - cats
 - hydrocarbons


 

   natural aphrodisiacs      