Former White House top Russia adviser Fiona Hill testified Thursday that it is "not credible" that EU Ambassador Gordon Sondland did not understand that the investigation President Trump was pushing for into Ukrainian natural gas company Burisma was equivalent to an investigation of the Bidens.

The exchange:

REP. MALONEY: "I thought you said it was obvious to you. Excuse me."

HILL: "It was obvious to me, correct."

MALONEY: "It was obvious Burisma meant Bidens."

HILL: "Yes, it was."

MALONEY: "You treated that as an easy thing to understand. Mr. Morrison figured it out with a single Google search. Is it credible to you that Mr. Sondland was completely in the dark about this all summer? I mean you had an argument about it."

HILL: "It is not credible to me that he was oblivious."

Why it matters: Sondland and former U.S. special envoy to Ukraine Kurt Volker both testified that they did not understand the Burisma investigation to be related to the Bidens until September, when the White House released the transcript of a phone call showing Trump discussed the Bidens with Ukrainian President Volodymyr Zelensky.

This is in spite of the fact that Rudy Giuliani was frequently tweeted and appearing on Fox News to push allegations about the Bidens and Burisma.

Sondland and Volker both said that if they had known Trump was pushing for an investigation of his domestic political rival, they would have objected.

The big picture: One of the main takeaways from Hill's testimonies is that she had a conflict with Sondland over his claim that he was working on Ukraine policy at Trump's direction.

Hill testified that Sondland claimed to be reporting directly to the president and other senior White House officials to pursue a "domestic political errand" — investigations linked to the Biden family's business dealings in Ukraine — while National Security Council staff focused on traditional foreign policy.

Go deeper: More highlights from Hill's and David Holmes' testimony