Why does the speed of a sound wave increase as it moves into deep water?

a. because sound waves travel faster as water temperature decreases, and water temperature decreases with depth.
b. because sound waves travel faster in denser media, and water density increases with depth.
c. because sound waves travel faster as salinity decreases, and salinity decreases with depth.
d. because sound waves travel faster as the amount of phytoplankton decreases, and the amount of phytoplankton decreases with depth.

The speed of a sound wave increase as it moves into deep water because sound waves travel faster as salinity decreases, and salinity decreases with depth.

Explanation:

Salinity, Temperature and pressure affect the speed of sound travels in ocean. At a depth of 1000 m in mid latitudes the sound is minimum. Sun makes ocean warm and the temperature become increase in their surface so sound speed becomes fast.

The wave amplitude is related to its carried energy. The wave who amplitude is high carries huge amount of energy and same low amount of amplitude wave carries low amount of energy.