US STOCKS-S&P 500 posts worst day since Oct; energy shares sink By: Reuters: Company News December 08, 2014 at 16:49 PM EST * Indexes: Dow off 0.6 pct, S&P 0.7 pct, Nasdaq down 0.8 pct (Updates to close) Read More >> Related Stocks: Apple ConocoPhillips Gopro Inc Cl A McDonald's Corp Merck & Co