Explain the working principle of a clinical thermometer ​

A thermometer works on the principle that solids and liquids expand on heating. As the temperature rises, mercury expands causing it to move upwards and depict the temperature. ... As the temperature of the bulb rises, the liquid expands up the tube through the constriction.Jun 22, 2018

Explanation:

A clinical thermometer is a thermometer used to measure human body temperature. Most made in the 20th century are mercury-in-glass thermometers. They are accurate and sensitive, having a narrow place where the mercury level rises very fast. A kink in the tube stops the mercury level from falling on its own.

the answer is option a.