The next big witness for the House Democrats’ impeachment hearings is Marie Yovanovitch, the former American ambassador to Ukraine who was recalled last spring at President Trump’s insistence.

It is unclear what firsthand knowledge she will offer about the core allegation of this impeachment: that Trump delayed foreign aid assistance to Ukraine in hopes of getting an investigation of Joe Biden and Democrats started.

Nonetheless, she did deal with the Ukrainians going back to the summer of 2016 and likely will be an important fact witness.

After nearly two years of reporting on Ukraine issues, here are 15 questions I think could be most illuminating to every day Americans if the ambassador answered them.