People gather around a car as it is removed by a mobile crane in Tehran, Iran. The car was being driven by Iranian nuclear scientist Mostafa Ahmadi Roshan when it was targeted by a bomb Wednesday. Roshan was killed in the blast. Meghdad Madadi/AP hide caption

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An oil platform in the Norwegian sea. Marcel Mochet/AFP/Getty Images hide caption

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An oil drilling rig is seen near Ray, N.D., last September. The well is being drilled into the Bakken Formation, one of the largest contiguous deposits of oil and natural gas in the United States. Karen Bleier/AFP/Getty Images hide caption

itoggle caption Karen Bleier/AFP/Getty Images