The correct answer is: D. Sonometer.
A sonometer is an instrument used to study the behavior of a vibrating string. It consists of a string stretched between two supports, with a movable bridge that can be used to change the length of the string. The string is plucked, and the sound produced is analyzed by a microphone and amplifier. The frequency of the sound can be changed by changing the length of the string, the tension in the string, or the mass per unit length of the string.
A barometer is an instrument used to measure atmospheric pressure. It consists of a sealed container filled with a liquid, such as mercury or alcohol. The pressure of the atmosphere pushes down on the surface of the liquid, and the height of the liquid in the container is a measure of the pressure.
A hydrometer is an instrument used to measure the density of a liquid. It consists of a glass tube with a weighted bulb at one end. The tube is placed in the liquid, and the height
of the liquid in the tube is a measure of the density of the liquid.A hygrometer is an instrument used to measure the humidity of the air. It consists of a material that changes its electrical resistance or capacitance in response to the humidity of the air.
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