Which day is called the Black September day in Olympic history

September 5, 1972 is known as Black September day in the history of Olympics. on this day in Munich, The Palestinian terrorists invaded the Israeli quarters in the Olympic village and took several players as Hostage besides killing two on the spot.

11 more Israeli team mates lost their lives in an encounter between German police and Palestinians belonging to the Black September group. Many countries called for the immediate closure of the games but Olympics carried on.

why common salt becomes wet in rainy season

common salt is slightly hygroscopic in nature due to the presence of a small amount of magnesium chloride in it. when it is kept open in rainy season the magnesium chloride in it absorbs moisture from air and the salt gets wet.