Stocks pulled back sharply Monday, racking up their biggest losses so far for the year. It was also the major indexes' worst day since the Nov. 23 follow-through. The Nasdaq slid 1.5%, hurt by declines in heavyweights Apple (AAPL), Google (GOOG) and Oracle (ORCL). Database software giant Oracle fell 3% on news that it would acquire Acme Packet (APKT). Meanwhile, the S&P 500 dropped 1.2% and closed below the 1500 level. Round numbers can mark key