What are the two main factors that affect the velocity of sound in seawater?

The correct choice identifies the two main factors that significantly influence the velocity of sound in seawater: temperature and salinity.

Temperature affects sound velocity because as water temperature increases, its molecules move more rapidly, allowing sound waves to travel faster. This increased molecular activity enhances the propagation of sound through the water. The relationship is not linear, but generally, a rise in temperature correlates with an increase in sound velocity.

Salinity also plays a crucial role; as salinity increases, the density of seawater increases, which can also contribute to an increase in sound velocity. The higher concentration of dissolved salts affects the physical properties of water, altering how sound waves move through it.

While pressure and density are relevant in discussing sound in fluids, the direct impact of salinity and temperature is more pronounced with regard to sound velocity in seawater. Other factors like wave frequency and amplitude relate more to the characteristics of sound waves rather than their speed, and current and depth can have indirect influences but aren’t primary factors in determining the basic velocity of sound in the marine environment.