The Cboe Volatility Index, an options-based gauge of expected volatility in the S&P 500 widely known by its trading symbol, VIX, jumped Monday morning to its highest level since December.

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The Cboe Volatility Index, or VIX, climbed to 22.78 on Monday. That is its highest closing level since the day after the Federal Reserve’s December meeting, when the central bank’s wait-and ...