Falling for the second straight on monday, the Sensex at the Bombay Stock Exchange plunged 363 points, or 1.8 percent, to close below the 20,000 mark, at 19,901, on rate hike concers. The Nifty dropped 122 points, or 2 percent, to 5,890.Stock markets in China, Hong Kong, South Korea and Singapore ended mixed. The rupee weakened 37 paise, to 62.60 against the dollar.Falling for the third straight day, gold lost 250 rupees, to 30,250 rupees per ten grams in Delhi. Silver declined 475 rupees to 49,025 rupees per kilo.And Brent crude oil futures stood above 109 dollars a barrel, while US crude gained 19 cents, to 104.94 dollars a barrel.