Given an open-ended topic (movie name, a persons name, an event, sports, etc) generate a simple trivia-type question.

cuba libre
What specifically is the alcoholic ingredient of the drink Cuba Libre?

the history of the decline and fall of the roman empire
Who wrote The Decline and Fall of the Roman Empire between 1772 and 1787 (published from 1776 to 1789) in 6 volumes?

angle

In geometry, which unit is defined as being equal to the angle subtended at the centre of a circle by an arc equal in length to the radius ?