I answered "the theft" from WordReference.
This is my first exposure to "le vol" in this Duolingo course. The word does not appear in the "tips" for this test. Nor did it appear in any of the previous tips or tests.
Note that I do the tests from top to bottom in the list of tests, without missing any.
I think it's unfair to spring a new word on students in the middle of a test.