Where is air almost completely humidified? in the lungs in the trachea in the alveoli in the nose?

None of the provided choices provide a completely correct answer. In fact, 75% of humidification takes place in the nose and mouth, with the rest taking place in the trachea. When you breath in, mucous membranes inside the nose and mouth release moisture to air. It is estimated that the average adult evaporates 200 to 300 ml of water per day during this process. The process is very efficient: while  breathing in through nose or mouth, the mucous membranes are cooled down.  During breathing out, this cooling effect causes condensation of some of the moisture in the air coming from the lungs, thereby moisturizing the mucous membranes