The benchmark Sensex on Bombay Stock Exchange On Wednesday staged the biggest rally in almost two months to end the day higher close to 540 points on aggressive buying by funds, triggered by government's bullish forecast on the economy and positive global trends. The 30-share Sensex posted a sharp rise to settle the day at 17,231. This is the biggest rally since November 4, when it gained 524 points.Wider National Stock Exchange index Nifty also spurted by 158 points to close at 5,144. It touched the day's high of 5,150 points. Marketmen say, a sharp rebound in Asian and European stock markets following a strong US data and expectations of a speedy recovery in the US economy, further boosted the market sentiment.