Equal sensitivity from linear scales and equal range

Steps:

• Thermometers P and Q are identical except P has less mercury, affecting expansion volume.
• Equal range means both cover the same temperature span from lowest to highest.
• Linear scales ensure uniform division of temperature intervals along the scale.
• Thus, scale reading change per degree is identical, yielding equal sensitivity.

Why C is correct:

• Sensitivity is the scale deflection per unit temperature change; linear scales with equal range ensure this ratio is the same by definition.

Why the others are wrong:

• A: Less mercury in P alters contraction, potentially raising its lowest measurable temperature.
• B: This restates the given information, not an inference about the thermometers' properties.
• D: Not enough information.

Final answer: C