Hygrometer is used to measure

The correct answer is: B. relative humidity.

A hygrometer is an instrument used to measure the amount of water vapor in the air. It is often used to measure the relative humidity, which is the ratio of the amount of water vapor in the air to the maximum amount of water vapor that the air can hold at a given temperature.

The purity of milk is measured by a variety of methods, including the Babcock test, the Gerber test, and the Soxhlet test. The specific gravity of a liquid is a measure of its density relative to the density of water. It is calculated by dividing the density of the liquid by the density of water.

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