The Sensex at the Bombay Stock Exchange jumped 123 points, or 0.7 percent, to 17,503, amid easing food inflation, on clearing day in the derivatives segment, today. The Nifty at the National Stock Exchange gained 39 points, or 0.7 percent, to 5,254.Stock markets in China, Hong Kong, and South Korea slipped between 0.3 percent and 1 percent.