Jacobson's organ, also known as vomeronasal organ is an organ of chemoreception and part of olfactory system. These are present in many animals and help them to smell things. These are present in the form of patches of sensory cells in the nasal chamber. They lie close to the nasal bone. These organs are named after their discoverer, Ludvig Levin Jacobson.
So, the correct answer is 'Smell'.