The apparatus used to measure humidity of atmosphere is :

Options

A. Hydrometer
B. Hygrometer
C. Gravimeter
D. Manometer

Explanation

To determine the apparatus used to measure the humidity of the atmosphere, we can analyze the options provided:

1. **Hydrometer**: This instrument is used to measure the specific gravity or relative density of liquids. It is not used for measuring humidity. Therefore, this option is incorrect.

2. **Hygrometer**: This is the correct instrument used to measure humidity in the air or atmosphere. It is specifically designed for this purpose, making it the right choice.

3. **Gravimeter**: This device measures the force of gravity at a specific location. It is not related to humidity measurement, so this option is also incorrect.

4. **Manometer**: A manometer is used to measure the pressure of gases or liquids. It does not measure humidity, making this option incorrect as well.

After analyzing all the options, the correct answer is:

**The apparatus used to measure humidity of the atmosphere is: Hygrometer.**

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