https://finance.yahoo.com/news/battered-stock-traders-brace-1-201500641.html
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Going into Friday, expiring S&P 500 options showed the highest concentration in the 4,000 strike, with over 93,000 open positions set to run out. That includes 41,024 calls and 52,269 puts.
Should the S&P 500 close well below 4,000 Friday, that could set the stage for a bounce Monday as dealers who brokered these options and were short stocks to neutralize their positions would need to unwind that hedge, according to Brent Kochuba, founder of analytic service SpotGamma. In other words, market makers will be free to buy back stocks to cover the short exposures that are no longer needed.---------------