Here's why:

* External Respiration: This refers to the exchange of gases between the air in the lungs and the blood.

* Lungs: The lungs are the primary organs responsible for this exchange. Their tiny air sacs (alveoli) provide a large surface area for oxygen to diffuse into the blood and carbon dioxide to diffuse out.

While other organs play supporting roles (like the heart for circulation and the diaphragm for breathing), the lungs are the central organ for external respiration.