Concept:The nose conditions the air we breathe in by warming and moistening it.Explanation:The nasal cavity has a rich blood supply and a mucous lining.These warm the inhaled air and add moisture to it.This prepares the air before it travels to the trachea and lungs.The epiglottis mainly prevents food from entering the windpipe.The trachea is a passage for air but does not primarily warm or moisten it.The mouth lacks the specialised moist lining that the nose provides.Answer:B. nasal cavity