A Levels Biology (9700)•9700/11/O/N/23

Explanation
Surface area:volume ratio increases with more extreme cylinder shapes for fixed volume
Steps:
- Recall SA/V = 2/r + 2/h for a cylinder.
- Assume equal volume, so h ∝ 1/r²; ratio = 2/r + 2r² (normalized V=π).
- Z has balanced r and h (e.g., h≈r), minimizing ratio via calculus (derivative zero at optimal r).
- X is tall/thin (small r, large h), giving moderate ratio; Y is short/fat (large r, small h), giving largest ratio.
Why C is correct:
- C orders from smallest to largest ratio (Z balanced < X tall/thin < Y short/fat), matching formula where extremes increase SA/V relative to balanced shape.
Why the others are wrong:
- A reverses order, ignoring balanced minimum.
- B swaps X and Z, underestimating thin cylinder's ratio.
- D starts with medium Y, missing Z's lowest ratio.
Final answer: C
Topic: Cells as the basic units of living organisms
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