The BSE benchmark Sensex rose marginally by 10 points in the opening trade in on selective buying by funds and retailers.The 30-share barometer, which had gained 111.13 points in the previous session, rose by 10.41 points, or 0.05 per cent, to 18,804.Similarly, the wide-based National Stock Exchange index Nifty moved up by 1.25 points, or 0.02 per cent, to 5,718.40.