Inhaled air is made warm and moist in the

Step 1: Analyze the question We're asked which part of the respiratory system warms and moistens air as it is breathed in.

Step 2: Explain the concept Air must be warmed and moistened before it reaches the delicate lungs. Cold, dry air would damage the alveoli. The nasal cavity is specially built for this:

• It has a rich supply of blood capillaries near the surface, which release heat and warm the air.
• Its lining (mucous membrane) has mucus-secreting cells, so the moisture from the mucus humidifies the air.
• It also has hairs and mucus that trap dust and germs, so the air is filtered as well.

Step 3: Check each option

• A. Epiglottis: This is a flap of cartilage that covers the trachea during swallowing so food does not enter the windpipe. It does not warm or moisten air.
• B. Nasal cavity: Correct. It warms, moistens and filters air.
• C. Trachea: It is lined with ciliated, mucus-secreting cells that trap dust and push it upward. It does contribute a little moisture, but the main warming and moistening happens earlier, in the nose.
• D. Mouth: Air can enter through the mouth, but the mouth lacks the specialized lining and rich capillary network, so air breathed this way is not properly warmed or moistened. This is why breathing through the nose is healthier.

Step 4: Answer The correct option is B. nasal cavity.

Tip: Remember "Nose = Filter, Warm, Moisten." If a question asks where air is conditioned before reaching the lungs, think nose first. Also link the epiglottis with swallowing, not breathing.