The swelling in feet and ankles of an aged person due to sitting continuously for long hours during travel, is reduced by soaking the feet in warm salt water. This is because of

Soaking feet in warm water promotes the osmosis of molectules, including fluids, by increasing their kinetic energy. It also facilitates the movement of molecules from an area of higher concentration (swollen tissues) to an area of lower concentration (the bloodstream). This helps in reducing swelling by removing exeess fluid and promoting proper circulation.