The loudness of the sound is measured in _ _ _ _ _ _.
A. Decibels
B. Meters
C. Kilograms
D. Seconds

Hint: The loudness of the sound defines its intensity. Both intensity and loudness have different units. To identify the correct option, check the every given option.

Complete answer:
To answer this question, let’s define the loudness of the sound. The loudness of the sound defines its intensity. If the amplitude of the sound is large so loud the sound is. We know that the loudness of sound is proportional to the square of the amplitude of the sound wave. To identify the unit of loudness from the given options, let’s check every option one by one as follows,
The loudness of the sound is expressed in decibels (dB). In everyday life, we hear unbearable sounds called noise. The loudness of such noise is generally greater than 80 dB. The loudness of our normal conversation is around 60 dB. Therefore, the option (A) is correct.
We know the S.I unit of displacement, length, and height is meter. Therefore, the option (B) is incorrect. We know that the S.I unit of mass is kilogram. Therefore, the option (C) is incorrect. We express the time period in seconds. Therefore, the option (D) is incorrect.

So, the only correct answer is option (A).

Note: Loudness does not mean the intensity of sound or amplitude of the sound. It is the property of sound which is related to the intensity and amplitude of the sound wave. Remember, the unit of intensity of sound is bel.