The graphs below show the change in temperature and salinity of a region of ocean as an instrument is lowered below the surface. Depth is measured in kilometers below the surface, temperature in degrees Celsius, and salinity in parts per thousand. What is the most valid conclusion regarding ocean salinity based on the data?

A. Ocean salinity is not related to water temperature.
B. Ocean salinity changes with depth at a steady rate throughout the entire water column.
C. Ocean salinity increases as ocean temperature decreases.
D. Ocean salinity is more stable at higher temperatures than at lower temperatures.