The blood coming out of the lungs is richer in which of the following compared to the blood entering the lungs?

Body cells must continuously receive $P$ and release $Q$ produced by the cells. What are $P$ and $Q$ in the given statement?
$P \quad Q$

The partial pressure of oxygen in the alveolar air is

What is the value of $pCO_2$ in atmospheric air,alveoli,and tissues respectively?

Maximum amount of oxygen is lost from the blood in the

Given below are two statements.
Statement $I$: Respiratory membrane is composed of two layers of squamous epithelia,each resting on a thick basement membrane.
Statement $II$: The diffusion of a respiratory gas takes place from lower partial pressure to higher partial pressure of the same.
In the light of above statements,choose the most appropriate answer from the options given below: