Oxygen's Path in the Respiratory System

Steps:

• Air enters through the trachea, the main airway from the mouth/nose.
• It branches into bronchi, then smaller bronchioles, distributing air deeper into lungs.
• Oxygen reaches alveoli, tiny air sacs where gas exchange occurs.
• Oxygen diffuses across alveolar walls into surrounding pulmonary capillaries, entering the blood.

Why D is correct:

• This sequence follows the anatomical pathway defined in respiratory physiology, where oxygen travels from trachea to bronchi to bronchioles to alveoli before diffusing into capillaries for blood transport.

Why the others are wrong:

• A: Reverses the flow, starting from alveoli instead of entry point.
• B: Incorrectly places capillaries before alveoli, ignoring gas exchange order.
• C: Jumbles the path with trachea and bronchi after capillaries, defying airflow direction.

Final answer: D