The word that provides the best context clue to the meaning of churning is turning.
Sometimes the word sweet is used for emphasis in phrases or exclamations. Ex :sweet nothings here she is sad about the parting, hence the sorrow. She id sad to part from romeo
They made a huge profit by doing things the proper way.
The answer is: Impromptu speeches require lots of research.
When you Impromptu, it means that it was not prepared ahead of time. Usually it requires stock information. Research could not be used in impromptu speeches as it is something that is done without preparation.