Answer:
The correct answer is - thermometer.
Explanation:
A thermometer is an instrument that is used to measure the temperature or the difference between the temperature. A medical thermometer or the clinical thermometer is used to measure the temperature of the body or the. It is a glass thermometer that has a sensor or the part that is changed due to the temperature change and a numeric part that tells about the numeric value of the increase in temperature.
This tool can be used to measure the body temperature in the experiment of Carl. It can be put in the mouth under the tongue, in armpits and rectal opening.
Thus, the correct answer is - Temperature.