The Sensex at the Bombay Stock Exchange fell 128 points to trade at 19,870 a shortwhile ago. The fall was attributed to profit-booking by funds and retail investors after recent gains, amid a mixed trend in the Asian region. The 30-share index had rallied over 1,750 points in the previous four sessions.The Nifty at the National Stock Exchange also declined by 31 points to trade at 5,866.