WATCH: Senate asks questions during President Donald Trump’s impeachment trial

WASHINGTON (AP) -- Senators in President Donald Trump's impeachment trial have posed dozens of questions to White House lawyers and to House Democrats prosecuting the case.

WATCH:

There were questions about quid pro quos and whisteblowers, the Constitution and an unpublished book.

The questions, written on paper and read aloud by Chief Justice John Roberts, provide a window into the thinking of senators who until now had been silent inside the chamber.