Answer:
Mary is correct because as the liquid cools, the molecules slow down as they lose kinetic energy.
Explanation:
The way to identify the temperature of a body, according to common sense, is to use the words hot and cold, but in fact, hot is when the molecules are very agitated, causing an increase in body temperature. The cold is related to the more stationary state of the molecules, the less agitated, the colder the body becomes.
With that, we can say that as the liquid cools, the molecules move less and less, which decreases their kinetic energy, which is the energy related to movement. In this case, Mary is correct because, as the liquid cools, the molecules slow down as they lose kinetic energy.
the wavelength of the wave. 
and 
, we can find the value of the frequency: