The Sensex at the Bombay Stock Exchange gained 66 points–or 0.4 per cent—to close at 17,750 after a special 90-minute trading session today. It had gained 371 points in the last two trading sessions.The Nifty at the National Stock Exchange rose 17 points–or 0.3 percent– to 5,359.Sentiment remained bullish as the European Central Bank's new bond buying plan is likely to lower the borrowing costs for the euro zone's debt-ridden nations and ease fears over the euro's fate. Both the stocks exchanges were open for a special session, from 11.15 am to 12. 45 pm, to test their disaster recovery sites.