The BSE benchmark Sensex fell by nearly 31 points in early trade today as funds and investors adopted a cautious approach ahead of RBI policy meeting amid a weak Asian trend.The 30-share barometer fell by 30.86 points, or 0.15 percent, to 20,072.49 with stocks of oil and gas, consumerdurable and realty trading in the negative.The wide-based National Stock Exchange index Nifty declined by 7 points, or 0.12 per cent, to 6,067.80.