The Sensex at the Bombay Stock Exchange surged 376 points-its biggest single-day gain in seven weeks-to close above the 21,000-level, at 21,134, today, on hopes that the Reserve Bank will keep interest rates unchanged, and that the US central bank will not further trim its monetary stimulus anytime soon. The Nifty at the National Stock Exchange jumped 101 points, or 1.6 percent, to 6,273.Stock markets in China, Hong Kong, South Korea and Singapore ended mixed.