Key factors for efficient diffusion

Steps:

• Identify features typically required for diffusion: short diffusion distance (1), steep concentration gradient (2), and thin membrane or small particle size (3).
• Recall Fick's law: rate of diffusion proportional to surface area, concentration difference, and inversely to distance/thickness.
• Evaluate choices: all three features enhance diffusion rate per the law.
• Confirm A includes all essential features.

Why A is correct:

• Fick's first law (J = -D * ΔC / Δx) requires short distance (1), high gradient (2), and permeability via thin barriers/small solutes (3) for efficiency.

Why the others are wrong:

• B omits 3, ignoring permeability's role in crossing barriers.
• C omits 2, as low gradient slows diffusion despite short distance.
• D omits 1, as long distances hinder net movement even with gradient and permeability.

Final answer: A