SAN FRANCISCO — Congress has plenty of questions for Facebook CEO Mark Zuckerberg, who will testify on Capitol Hill Tuesday and Wednesday about the company's ongoing data-privacy scandal and how it failed to guard against other abuses of its service.

Facebook is struggling to cope with the worst privacy crisis in its history — allegations that a Trump-affiliated data mining firm may have used ill-gotten user data to try to influence elections. Zuckerberg and his company are in full damage-control mode, and have announced a number of piecemeal technical changes intended to address privacy issues.

But there's plenty the Facebook CEO hasn't yet explained. Here are five questions that could shed more light on Facebook's privacy practices and the degree to which it is really sorry about playing fast and loose with user data — or just because its practices have drawn the spotlight.

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QUESTION: You've said you should have acted years ago to protect user privacy and guard against other abuses. Was that solely a failure of your leadership, or did Facebook's business model or other factors create an obstacle to change? How can you ensure that Facebook doesn't make similar errors in the future?

CONTEXT: Zuckerberg controls 59.7 percent of the voting stock in Facebook. He is both chairman of the board and CEO. He can't be fired, unless he fires himself. "At the end of the day, this is my responsibility," he told reporters on a conference call last week. He also admitted to making a "huge mistake" in not taking a broad enough view of Facebook's responsibility in the world.

Zuckerberg, however, has been apologizing for not doing better on privacy for 11 years . In the current crisis, neither he nor chief operating officer Sheryl Sandberg have clarified exactly how Facebook developed such a huge blind spot, much less how it can prevent history from repeating itself.

POSSIBLE FOLLOW-UP: Does Facebook need a chief privacy officer with the authority to take action on behalf of users?

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QUESTION: Who owns user data on Facebook, the company or the users? If it's the latter, why shouldn't Facebook allow people to opt out of being targeted by ads?

CONTEXT: Facebook collects data on its own (your likes, which ads you click on, etc.); keeps data you share yourself (photos, videos, messages); and correlates data from outside sources to data on its platform (email lists from marketers, and until recently, information from credit agencies).

Who owns what is a difficult question to answer, and Facebook clearly hasn't been good at explaining it. While you can download everything the company knows about you, it doesn't really allow you to take "your" data to a rival.

Sandberg told Today's Savannah Guthrie that given Facebook's ad-driven business model, you can't currently avoid data mining of your public profile information. (You can opt not to see the resulting targeted ads , though.) Allowing that, Sandberg said, would effectively require Facebook to turn into a "paid product" that charges users.

POSSIBLE FOLLOW-UP: Don't other businesses allow some users to opt out of ads? Why can't Facebook charge users who want ad-free experiences the way Hulu and YouTube do?

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QUESTION: Facebook has made connecting with others and sharing information dead simple. Why haven't you put similar effort into making your privacy controls equally easy to use?

CONTEXT: Facebook has updated its privacy settings seven times in the last decade, each time aimed at making them simpler to use.

The latest update was on March 28. On April 4, the company announced new technical changes designed to close loopholes that allowed third parties overbroad access to user data.

Facebook makes many pieces of information your profile public by default; to lock them down, you have to change those settings yourself.

POSSIBLE FOLLOW-UP: Does this legacy suggest the government needs to step in with clear and universal privacy rules?

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QUESTION: Did Facebook threaten legal action against the Guardian newspaper in the U.K. regarding its reporting on the Cambridge Analytica scandal?

CONTEXT: John Mulholland, editor of the Guardian US, tweeted in March that Facebook had threatened to sue to stop publication of its story that broke the Cambridge Analytica scandal in mid-March. Neither the Guardian nor Facebook have commented further.

POSSIBLE FOLLOW-UP: Do you still stand behind Facebook's actions here?

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QUESTION: Have you spoken with critics, including some former Facebook investors and colleagues, who argue that the company's service has become an addictive and corrosive force in society?

CONTEXT: Sean Parker, Facebook's first president, said Facebook specializes in "exploiting" human psychology and may be harming our children's brains. An early investor in Facebook, Roger McNamee compared Facebook to an addictive substance such as nicotine and alcohol.

Brian Acton, a co-founder of WhatsApp (acquired by Facebook in 2014), recently recommended that people should delete their Facebook accounts . Chamath Palihapitiya, an early vice president at Facebook, said Facebook's tools are "ripping apart the social fabric."

POSSIBLE FOLLOW-UP: If not, why not?