Falling for the third straight session, the Sensex at the Bombay Stock Exchange dropped 183 points, or 1 percent, to 17,639, on Thursday, as rising inflation raised concerns of an imminent rate hike by the Reserve Bank. The Nifty at the National Stock Exchange fell 49 points, or 0.9 percent, to 5,274.Stock markets in Japan, China, Hong Kong, Singapore and South Korea ended mixed.