How men first learnt to __ words is unknown; in other words, the origin of language is a mystery. (create/invent)
Far be it from me to suggest a course of action in a situation like this.
On further reflection I have to say that this question doesn't make any sense at all. We don't speak of people learning to either create or invent. We think of people as inventing or creating because it's in their nature or they have a talent for it. No one goes to school to
learn to be creative or inventive. They may go to school to develop and refine their creative or inventive abilities but not to acquire them.
Still, as you say, you have to deal with the situation as you find it, so the "correct" answer stands I guess.