What type of direct reading thermometer works on the principle of thermal volumetric expansion of a liquid as the temperature rises and features a linear scale?

Correct Answer: Option B — Liquid-in-glass thermometer

Liquid-in-glass thermometers utilize the principle of thermal expansion, where a fluid like mercury or alcohol expands linearly within a calibrated tube as temperature increases. This direct-reading method provides a reliable, mechanical indication of temperature, commonly used in engine room auxiliary systems for monitoring cooling water or lube oil temperatures.