Answer:
B. In mercury, the frequency of the wave is the same as in ethanol, but the wavelength is greater.
Explanation:
To solve this easily, we can just calculate the wavelength of the sound in Ethanol and in Mercury.
In Ethanol, the wavelength will be:
λ = c/f
λ = 1160/440
λ = 2.63 m
In Mercury, the wavelength will be:
λ = c/f
λ = 1450/440
λ = 3.3 m
The wavelength of sound is greater in Mercury than in Ethanol but the frequency is the same.
Frequency of sound is not dependent on medium, but velocity and wavelength change depending on the medium.