U.S. stocks gained slightly this morning after the first back-to-back weekly losses since January for the Standard & Poor???s 500 Index, as small-cap shares advanced amid merger activity. AT&T Inc. (NYSE: T) dropped 2 percent after agreeing to buy DirecTV, the largest U.S. satellite-TV company. Pfizer Inc. (NYSE: PFE) jumped 1.6 percent after AstraZeneca Plc (NYSE: AZN) rejected the drug maker???s $117 billion offer. Campbell Soup Co. lost 3.1 percent after lowering its sales forecast for the year. The S&P 500 gained 0.1 percent to 1,878.87 at 10:04 a.m. in New York. The Dow Jones Industrial Average dropped 20.93 points, or 0.1 percent, to 16,470.38. The Russell 2000 Index added 0.3 percent. Trading in S&P 500 companies was 13 percent below the 30-day average for this time of day.