Sea water is saltier than rain water because rivers wash away salts from the earth and pour them into the sea. Option 1 correctly explains the reason behind the higher salinity of sea water. As rivers flow over the land, they pick up dissolved salts from rocks, soil, and other sources. This water, along with the salts, eventually reaches the sea and increases its salt content. On the other hand, rainwater is formed through the process of evaporation, where water vapor condenses and falls to the ground as precipitation. Unlike rivers, rainwater does not come in contact with the same sources of dissolved salts, resulting in lower salinity levels. Therefore, Option 1 provides the most logical and accurate explanation for the difference in saltiness between sea water and rain water.