The path followed by air as it passes through the lungs in mammals is

Step 1: Analyze the question The question asks for the correct order in which inhaled air travels through the respiratory passages of a mammal, from the outside toward the site of gas exchange.

Step 2: Explain the concept The respiratory tract works like a tree that branches into smaller and smaller tubes:

• Trachea (windpipe): the single large tube that carries air down from the throat.
• Bronchi: the trachea divides into two bronchi (singular: bronchus), one going into each lung.
• Bronchioles: each bronchus divides into many smaller tubes called bronchioles.
• Alveoli: tiny air sacs at the ends of the bronchioles, where oxygen enters the blood and carbon dioxide leaves it.

Step 3: Solution Following the air from the nose or mouth inward:

Trachea → Bronchi → Bronchioles → Alveoli

Now check each option:

• A: Starts with the bronchi before the trachea, which is wrong.
• B: This is the reverse of the path, which is wrong.
• C: Trachea → bronchi → bronchioles → alveoli, which is correct.
• D: Puts the bronchioles before the bronchi, which is wrong, because the bronchi are the larger tubes and come first.

Step 4: Answer The correct option is C.

Step 5: Exam tip Remember the order from big to small: T-B-B-A (Trachea, Bronchi, Bronchioles, Alveoli). The tubes get narrower as air goes deeper, and the alveoli at the very end are the smallest, where gas exchange happens. For air leaving the body, simply reverse the order.