If salinity increased at the poles , water near the poles would ?

According to Plato, there would be increase in density and the water near the poles would presumably sink rapidly. More density means that there's a higher percentage of saline water. The saltiness and temperature of water determines density, so if salinity increased at the poles, water near the poles would sink rapidly.

The correct answer is a. we know this because n (hap) + n (hap) = 2n (dip).