Falling for the fourth straight session, the Sensex at the Bombay Stock Exchange lost48 points, or 0.3 percent, to 17,591, on continued selling by investors, amid concerns of a rate hike by the Reserve Bank. The Nifty at the National Stock Exchange shed 11 points, or 0.2 percent, to 5,263.Stock markets in Japan, China, Hong Kong, Singapore and South Korea lost between 0.3 percent and 1.5 percent.