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

Correct Answer: A. Cryometer
A cryometer is a thermometer specifically designed to measure very low temperatures, typically in cryogenic applications (temperatures below -150°C or 123 K). These are used in scientific research involving liquid gases like liquid nitrogen, helium, and hydrogen.
Explanation of Other Options:
• B. Bolometer:
A bolometer measures the intensity of radiation or heat. It is not used to measure temperature directly.
• C. Pyrometer:
A pyrometer measures high temperatures, often in industrial applications, such as furnaces and molten metals.
• D. Platinum resistance thermometer:
This thermometer uses the resistance of platinum to measure temperature, but it is typically used in the range of -200°C to +850°C, not specifically designed for very low temperatures.
Thus, the thermometer designed for very low temperatures is the cryometer.