A pyrometer is used to measure

atmospheric pressure
humidity
high temperature
density

The correct answer is (c). A pyrometer is used to measure high temperature.

A pyrometer is a non-contact thermometer used to measure the temperature of a surface. It does this by measuring the amount of infrared radiation emitted by the surface. Pyrometers are used in a variety of industries, including manufacturing, metalworking, and glassmaking.

Atmospheric pressure is the pressure exerted by the weight of the air above a given point on Earth’s surface. It is measured in units of pascals (Pa). Humidity is the amount of water vapor in the air. It is measured in percent relative humidity. Density is the mass of a substance per unit volume. It is measured in grams per cubic centimeter (g/cm3).