The Sensex at the Bombay Stock Exchange surged 305 points, or 1.7 percent, to 18,842, registering its biggest gain in over two months on across-the-board buying, after rating agency Moody's said India's rating outlook is stable. The Nifty at the National Stock Exchange spurted 92 points, or 1.6 percent, to 5,727.Stock markets in China, Japan, Hong Kong, South Korea and Singapore ended mixed.