The correct answer is salinity.Isohalines It is used on maps to show the salinity of different places. Hence, Option 4 is correct.The average salinity of the ocean is 3.5% or 35 parts of salt in 1000 parts of water.The salinity of the Great Salt Lake, (Utah, USA), the Dead Sea, and the Lake Van in Turkey are 220, 240, and 330 respectively.The oceans and salt lakes are becoming saltier as time goes on because the rivers dump more salt into them, while freshwater is lost due to evaporation.The more frequently drawn isopleths include:Isotherm (equal temperature)Isobar (equal pressure)Isohyets (equal rainfall)Isonephs (equal cloudiness)Isohels (equal sunshine)contours (equal heights)Isobaths (equal depths)