The other responder used in. I hadn't thought of that. Common usage would probably use "in" but what I have pointed out as a use is also possible. The point is that whatever you use, it must be a preposition.
Explanation: By could also be used if there is an extensively long series of events before that “end” occurs. Other than that, “in” is most commonly written.
I believe that Russel Baker humorously uses first-person point of view in "No Gumption' to describe the problems of the Great Depression, I would say the answer is A.
