Male dogs use pheromones in urine to mark their territory, and generally, pheromones are volatile substances. Given these facts, male dogs use what in their urine to mark their territory among the following options:
- hydrocarbons
 - volatile substances
 - kinetic energy
 - an area swollen with pus
 - Chemical energy
 - competing for resources
 - add a solute
 - Positive charges


 

  volatile substances       