Business: Indian stock markets opened with a flat trend on Friday. Sensex and Nifty remained range bound amid volatility in early trade as investors remained cautious near record highs. The 30-share BSE Sensex rose 239.89 points, or 0.28 per cent, to 84,644.35 by 9:34. Meanwhile, the 50-share NSE Nifty rose 59.85 points or 0.23 percent to 25,937.70.