Germany's Economy And Energy Minister Sigmar Gabriel Meets Tesla Motors Inc. Chief Executive Officer Elon Musk [Getty Images]

Elon Musk, billionaire and chief executive officer of Tesla Motors Inc., arrives for a news conference in Berlin, Germany, on Thursday, Sept. 24, 2015. Tesla Motors Inc. chief executive officer Elon Musk said revelations that Volkswagen AG cheated on diesel emission tests is "obviously bad," but that the issue the world should really be concerned about is carbon dioxide emissions. Photographer: Krisztian Bocsi/Bloomberg via Getty Images

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