সঠিক উত্তর হচ্ছে: River wash away salts from earth and pour them into the sea
ব্যাখ্যা:
Sea water is saltier than rain water because river wash away salts from earth and pour them into the sea. Rain water is mostly pure water. Sea water has salt (and other minerals) dissolved in it. Water evaporates from the sea to form clouds (which eventually cause rain) - but the salt is left behind in the ocean. Thus, you can't have salt-water rain.