What was the name later known to the Army as the B-17?

The B-17, a significant heavy bomber used by the United States Army Air Forces during World War II, was originally designated as the Boeing 299. This aircraft was notable for its role in strategic bombing missions and was one of the most iconic bombers of the war, earning the nickname "Flying Fortress" because of its defensive armament and ability to sustain heavy damage while still flying. The B-17’s effective design and powerful performance made it a vital tool in the Allied bombing campaign against Germany. The other options listed are recognized aircraft, but they do not relate to the B-17; for instance, the Douglas M-3 is an entirely different aircraft with no connection to the bomber, while the Lockheed P-38 is a fighter plane, and the McDonnell Douglas DC-10 is a commercial airliner, making none of them related to the B-17’s designation or development.