You are presented with the quiz "What do male dogs use to mark their territory?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "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". 

So, what's the best answer to the question?


 

 smell          