The diffusion membrane is made up of:

What will be the $pO_{2}$ and $pCO_{2}$ in atmospheric air as compared to alveoli?

Which of the following statements is correct regarding the diffusion capacity of gases?

What is the approximate percentage of oxygen in alveolar air (in $\%$)?

Which are the three main layers that form the diffusion membrane?

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: