Fick's Law governs alveolar oxygen diffusion Steps:

• Identify key factors from Fick's law: diffusion rate depends on surface area, membrane thickness, partial pressure gradient, and diffusion coefficient.
• Match to features: assume 1 = large surface area, 2 = thin membrane, 3 = steep partial pressure gradient, 4 = unrelated factor like blood flow.
• Eliminate options excluding essential factors (area, thickness, gradient).
• Select A as it includes all three core diffusion enablers.

Why A is correct:

• Fick's law states diffusion rate = (surface area × diffusion coefficient × partial pressure difference) / membrane thickness, so 1, 2, and 3 directly maximize oxygen transfer from alveolus to blood.

Why the others are wrong:

• B includes 4 (e.g., blood flow aids transport but not diffusion across membrane).
• C omits 2 (thin walls reduce diffusion distance, essential for efficiency).
• D excludes 1 and 3 (lacks area and gradient, ignoring primary drivers).

Final answer: A