A thermometer for measuring very low temperatures is called:
A. Cryometer.
B. Bolometer.
C. Pyrometer.
D. Platinum resistance thermometer.

Hint:-Temperature is the degree of hotness or coldness. When the energy of the system arises then the molecules also start to move in a haphazard manner this happens due to the excitation of energy and if the temperature decreases then the movement of the molecules decreases as there is very less energy in the system.

Complete step-by-step solution:
In this problem it is asked to tell the device which is used to measure very low temperature.
There are different devices that are used to measure different ranges of temperature and the device used to measure low temperature is known as Cryometer.
The correct answer for this problem is option A.
Additional information: The study of material at very low temperature is known as cryogenics and this study is very useful and has many applications in the field of technology. The study has many applications in the field of food freezing which helps us to save a lot of food material to get waste. A thermocouple is also a Cryometer which helps us to measure temperature of about 1K. A resistance thermometer is Cryometer which can be used for the temperature measurement of about 0.01K. Magnetic thermometers are also a type of Cryometer which are used to measure the temperature of about 0.001K. Nuclear-resonance thermometer is a type of Cryometer which can measure a temperature of 0.0000001K.

Note:- The study at very low temperature is known as cryogenics The study of cryogenics is the measurement around 0K. The study of cryogenics is very important in the area of space technology as the fuel present is stored in very low temperature.