Respiratory pathway: Arrange the following in the order that inhaled air follows until oxygen reaches the blood: B) Nostrils → C) Windpipe (trachea) → A) Lung → D) Blood Choose the correct sequence.

Introduction / Context:
In respiration, air enters through the nose, travels down the conducting airways, reaches the lungs where gas exchange occurs, and oxygen then passes into the blood. Ordering these structures correctly demonstrates understanding of the airflow path.

Given Data / Assumptions:

• B) Nostrils are the external entry.
• C) Windpipe (trachea) conducts air to bronchi and lungs.
• A) Lung contains alveoli for gas exchange.
• D) Blood receives oxygen by diffusion across alveolar membranes.

Concept / Approach:
Trace air from outside to inside and then to circulation: entry → conduit → exchange organ → transport medium.

Step-by-Step Solution:
Start at B) Nostrils.Proceed to C) Windpipe.Arrive at A) Lung.Finally to D) Blood.Sequence: B, C, A, D.

Verification / Alternative check:
Any order that starts with blood or lung before nostrils/windpipe contradicts the inhalation path.

Why Other Options Are Wrong:
They break the physical pathway or reverse cause–effect.

Common Pitfalls:
Confusing the windpipe with lungs; windpipe is a conduit, lungs are the exchange site.

Final Answer:
B, C, A, D