Arrange the organs/fluids in the human respiratory pathway from air entry to gas transport. (i) Lung (ii) Nostrils (iii) Windpipe (trachea) (iv) Blood

Introduction / Context:
Human respiration proceeds along a well-defined anatomical route from nose to alveoli and then into circulation.

Given Data / Assumptions:

• Nostrils admit air.
• Windpipe conducts to bronchi.
• Lungs exchange gases.
• Blood carries gases to tissues.

Concept / Approach:
Route: entry → conduit → exchange → transport.

Step-by-Step Solution:
1) (ii) Nostrils.2) (iii) Windpipe.3) (i) Lung (alveoli).4) (iv) Blood (haemoglobin binding).

Verification / Alternative check:
Breath path cannot start at lungs or blood logically.

Why Other Options Are Wrong:
Any reversal of nostrils→trachea→lungs is anatomically incorrect; blood cannot precede lungs in air entry path.

Common Pitfalls:
Confusing inhalation path with cellular respiration sequence.

Final Answer:
(ii), (iii), (i), (iv)