NEW YORK (AP) - Facebook CEO Mark Zuckerberg often came across as one of the smartest people in the room as he jousted with U.S. lawmakers demanding to know how and why his company peers into the lives of its 2.2 billion users.
    
But while some questions were elementary, others left Zuckerberg unable to offer clear explanations or specific answers.
    
Inquiries about how much personal information Facebook vacuums up on and off its social network seemed particularly vexing.
    
Zuckerberg was also vague about whether Facebook was a monopoly and whether it would offer an ad-free option, as well as about how the company could offer the same level of privacy protection to everyone.
    
In 10 hours of testimony, Zuckerberg often resorted to one response. "I can have our team get back to you afterwards."

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