ANS:B - solar evaporation

Common salt is commonly produced from sea water in India by the solar evaporation method. In this method, sea water is collected in large shallow ponds or pans, and then the water is allowed to evaporate under the heat of the sun. As the water evaporates, salt crystals begin to form and settle at the bottom of the ponds. Once a sufficient amount of water has evaporated, the remaining concentrated brine is drained away, leaving behind salt crystals. These salt crystals are then collected, washed, and dried to produce common salt. Therefore, the correct option is: solar evaporation