Red blood cell biconcave shape aids efficient oxygen diffusion

Steps:

• Identify the biconcave disc shape of red blood cells from the diagram.
• Recall that this shape relates to functions like gas exchange and blood flow.
• Evaluate each option: A focuses on capacity, B on speed, C on surface area, D on trapping.
• Select C as it directly matches the shape's role in maximizing diffusion.

Why C is correct:

• The biconcave shape increases surface area-to-volume ratio, enhancing diffusion of oxygen and carbon dioxide per Fick's law of diffusion.

Why the others are wrong:

• A: Shape does not increase hemoglobin capacity; that's determined by cell volume.
• B: Shape aids flexibility for capillaries, not speed in arteries.
• D: Shape prevents trapping in narrow capillaries, not veins.

Final answer: C