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Members of the Saudi national guard man a checkpoint at a border post on the Saudi-Yemen border in Najran, Saudi Arabia, on Thursday, April 23, 2015. Speculators pulled bearish oil bets at the fastest pace on record as Saudi Arabia renewed strikes on Yemen and U.S. output slowed. Photographer: Glen Carey/Bloomberg via Getty Images

Members of the Saudi national guard man a checkpoint at a border post on the Saudi-Yemen border in Najran, Saudi Arabia, on Thursday, April 23, 2015. Speculators pulled bearish oil bets at the fastest pace on record as Saudi Arabia renewed strikes on Yemen and U.S. output slowed. Photographer: Glen Carey/Bloomberg via Getty Images