Concept:A wet and dry hygrometer is an instrument used to measure the amount of moisture present in the air.
Explanation:This hygrometer has two thermometers: a wet bulb thermometer and a dry bulb thermometer.
The wet bulb is covered with a wet cloth, while the dry bulb remains uncovered.
When air passes over them, moisture evaporates from the wet bulb and cools it.
The difference between the readings of the two thermometers shows how much water vapour is in the air.
A smaller difference means the air is more humid, and a larger difference means the air is drier.
In a brooder house, chicks need a suitable level of air moisture for healthy growth.
Therefore, the wet and dry hygrometer is used to monitor the relative humidity of the brooder house.
It is not used for measuring rainfall, temperature, or atmospheric pressure directly.
Answer:C. relative humidity