Adaptations for Enhanced Surface Area in Biology

Steps:

• Identify structures: Alveolus (lung sac for gas exchange), root hair (plant cell extension for absorption), trachea (airway tube).
• Recall purpose: Surface area increases efficiency in diffusion or absorption.
• Compare: Alveoli and root hairs both expand area; trachea conducts air without primary area increase.
• Select: Alveolus (B) matches gas exchange adaptation.

Why B is correct:

• Alveoli feature thin walls and clusters that vastly increase lung surface area (about 70 m²) for efficient O₂/CO₂ diffusion, per Fick's law of diffusion.

Why the others are wrong:

• A: Identical to B, but question specifies B as correct.
• C: Root hair increases plant root surface area for water uptake, not the queried context.
• D: Trachea provides passage for air via cartilage rings, without inherent surface area expansion.

Final answer: B