Which surface of a plant leaf is better adapted for gas exchange?

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

What is the partial pressure of oxygen $(pO_2)$ in the alveoli of the lungs compared to the blood?

Maximum amount of oxygen is exchanged from the blood in the . . . . . . .

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

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: