Sensitivity in clinical thermometers depends on capillary scale length

Steps:

• Define sensitivity as the rise in liquid column per degree Celsius for precise readings.
• Note clinical thermometers have a fixed range (e.g., 35–42°C), so expansion volume is constant.
• Identify that longer bore length spreads this expansion over more distance, enabling finer graduations.
• Eliminate options unrelated to scale expansion or precision.

Why B is correct:

• Sensitivity equals liquid column height per °C, given by h = (Vα ΔT)/A; for fixed Vα ΔT (range), longer bore length increases h, improving resolution per the thermometer scale formula.

Why the others are wrong:

• A: Constriction traps mercury for reading retention but does not alter expansion distance.
• C: Glass tube diameter (outer) influences bulb volume indirectly but not capillary scale sensitivity.
• D: Glass thickness ensures durability and heat conduction but has no effect on liquid rise precision.

Final answer: B