The correct answer is: B. Depth.
A fathom is a unit of length equal to six feet (1.83 meters). It is used to measure the depth of water, especially in nautical contexts. The word “fathom” comes from the Old English word “faethm,” which means “embrace.” This is because a fathom was originally the distance between the outstretched arms of a man.
Sound is a wave that travels through a medium, such as air or water. The frequency of a sound wave is the number of waves that pass a given point in a given amount of time. The unit of frequency is the hertz (Hz).
Distance is the length of a path between two points. The unit of distance is the meter (m).
Frequency is not a unit of depth.