Which of the following method is most appropriate?
(1) a          (2) b
(3) c          (4) d

Understanding the graph

• X‑axis: glucose concentration (mg/dL).

• Y‑axis: biosensor signal.

• Clinically relevant range: 80–250 mg/dL.

• A good method should be:

  • Sensitive (steep slope) within 80–250 mg/dL.

  • Not saturated throughout most of this range.

  • Linear or smoothly monotonic for accurate quantitation.

Analysis of each curve

• a: Very steep rise at low glucose and then saturates early, so much of 80–250 mg/dL lies on the plateau. Poor for distinguishing higher values.

• b: Starts responding near 80 mg/dL and rises steeply, remaining unsaturated through most of 80–250 mg/dL, giving good sensitivity and usable dynamic range.

• c: Very shallow slope over 80–250 mg/dL; sensitivity is too low, so small changes in glucose give small signal changes.

• d: Response kicks in late (closer to upper end), so it is insensitive at normal/low‑normal levels around 80–120 mg/dL.

Therefore, method b offers the best combination of sensitivity and usable dynamic range across 80–250 mg/dL, making option (2) b the correct choice.