Rep. Alexandria Ocasio-Cortez grilled Facebook CEO Mark Zuckerberg during his congressional testimony Wednesday, and he struggled to come up with responses to her questions.

The New York congresswoman asked Zuckerberg questions about fact-checking political advertisements on the site and who was approved to be a third-party fact-checker.

Other politicians, including the 2020 presidential candidates Sen. Elizabeth Warren and former Vice President Joe Biden, have criticized Facebook's fact-checking policies when it comes to political ads.

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Rep. Alexandria Ocasio-Cortez grilled Facebook CEO Mark Zuckerberg during his congressional testimony Wednesday, and he struggled to come up with responses to her questions.

Zuckerberg sat before the House Financial Services Committee as the congresswoman from New York asked him questions about fact-checking political advertisements on the site, whose policy has faced criticisms from other politicians like the 2020 presidential candidates Sen. Elizabeth Warren and former Vice President Joe Biden.

"Would I be able to run advertisements on Facebook targeting Republicans in primaries saying they voted for the Green New Deal?" Ocasio-Cortez asked during the hearing. "I mean, if you're not fact-checking political advertisements, I'm just trying to understand the bounds here."

"I don't know the answer to that off the top of my head," Zuckerberg said. As Ocasio-Cortez began to move to another question, he added, "I think, probably."

The social-media site confirmed earlier this month that such ads were allowed to run and that in most instances political ads would not be subject to fact-checking.

"Posts and ads from politicians are generally not subjected to fact-checking," according to Facebook's policy. "In evaluating when this applies we ask our fact-checking partners to look at politicians at every level."

Read more: Facebook announced that it will not pull down or fact check posts made by politicians

President Donald Trump reportedly spent $1.6 million on advertising on Facebook with misleading and debunked claims about former Vice President Joe Biden in relation to the whistleblower scandal in which the two politicians are entangled. Facebook did take down one of Trump's ads, but only because it featured Biden saying "son of a bitch," which violated the platform's policy on profanity.

"So you won't take down lies, or you will take down lies?" Ocasio-Cortez asked. "I think that's a pretty simple yes or no. I'm not talking about spin — I'm talking about actual disinformation."

"This is a democracy," Zuckerberg replied. "I believe people should be able to see for themselves what politicians they may or may not have voted for are saying and judge their character for themselves."

The Facebook CEO clarified that the site would take down any posts "calling for violence or could risk imminent physical harm or voter or census suppression."

"There will be some instances where a false or partly false rating from our fact-checking partners will affect politicians," Facebook's policy continues. "When a politician shares a specific piece of content — i.e., a link to an article, video or photo created by someone else that has been previously debunked on Facebook — we will demote that content, display a warning and reject its inclusion in ads."

The congresswoman proceeded to ask about Facebook's partnership with Check Your Fact, a subsidiary of The Daily Caller, which has been tied to white nationalists. Check Your Fact is one of six third-party organizations working with the social-media site to fact-check content.

Zuckerberg said Facebook did not appoint the organizations but instead worked with Poynter's International Fact-Checking Network, which he said had "a rigorous standard as to who they allow as a fact-checker."

A Facebook representative, Lauren Svensson, told Vox that "we do believe in having a diverse set of fact-checking partners."

Watch a clip of the testimony below: