U.S. stock-market indexes opened slightly lower Wednesday, with the S&P 500 and Nasdaq on track for a fourth consecutive session of declines. The weakness is mainly due to a continued selloff in the technology sector. The S&P 500 opened 3 points, or 0.1%, lower at 2,626. If the benchmark index ends lower, it would be the longest losing streak since March. The Dow Jones Industrial Average was off by 13 points, or less than 0.1%, at 24,165. The Nasdaq Composite index fell 25 points, or 0.4%, to 6,737. If the tech-heavy index closes lower, it would be the longest losing streak since November 2016. Among the best performers on Wall Street, shares of DaVita Group Inc jumped after news that UnitedHealth Group had agreed to buy the physician group for about $4.9 billion in cash.