U.S. stocks fluctuated as investors weighed growth prospects for the world s biggest economy amid rising bets on continuing policy support from the Federal Reserve.Biogen Inc. led health-care shares higher, helping to send the Nasdaq Composite Index to the highest in a year, after positive trial results for a drug the company is developing with Ionis Pharmaceuticals Inc., which rallied 35 percent.

Apple Inc. increased 1.2 percent to lift technology shares, while Exxon Mobil Corp. and Chevron Corp. dropped at least 1.6 percent as sliding crude prices dragged energy producers lower.

The S 500 Index rose 0.1 percent to 2,175.21 at 10:51 a.m. in New York, after its longest monthly winning streak since 2014.

The Nasdaq Composite added 0.5 percent, bolstered by gains in Apple, Biogen and Amazon.com Inc.

The Dow Jones Industrial Average lost less than a point, to 18,431.87.

The market s in that uncertain zone as we try to see what earnings do for us, said Bruce McCain, who helps oversee $35 billion as chief investment strategist at Key Private Bank in Cleveland.

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