ANS:A - bimetallic thermometer.

The temperature measurement method that employs the thermal expansion of a solid is a bimetallic thermometer. In a bimetallic thermometer, two different metals with different coefficients of thermal expansion are bonded together. When subjected to a change in temperature, the metals expand or contract at different rates, causing the bonded strip to bend. This bending motion is proportional to the temperature change, allowing the thermometer to indicate the temperature on a scale. Therefore, the correct option is: bimetallic thermometer.