The partial pressure of oxygen in the alveoli of the lungs is

Diffusion of gases occurs in the alveolar region only and not in the other parts of the respiratory system. Why?

Almost the same $pCO_{2}$ in humans is found in

In the given diagram representing the partial pressure of gases during pulmonary circulation, what are the partial pressures of $CO_2$ at $P$ and $Q$ respectively? (Assuming $P$ is deoxygenated blood entering the lungs and $Q$ is oxygenated blood leaving the lungs)

Which of the following statements is $NOT$ correct?

In which part does gaseous exchange take place in a rabbit?