Concept:Salinity is the concentration of dissolved salts in seawater; enclosed seas in hot, dry regions have higher salinity.Explanation:The Red Sea is located in a hot, arid region with high evaporation and little freshwater inflow.This makes its salinity very high, around 40‰.The Mediterranean Sea is also saline but lower than the Red Sea.The Caspian Sea is a brackish inland sea.The Baltic Sea has low salinity due to many rivers and cool climate.Answer:D. Red Sea