Detailed Instructions: In this task, you are given a text which is the body of a document. You are given a question and options. Pick the correct number. Don't generate anything else apart from the numbers provided in options.
Q: Context: The Douglas Cloudster was a 1920s American biplane aircraft. It was the only product of the Davis-Douglas Company; designed to make the first non-stop flight coast-to-coast across the United States.
Question: The document can be classified to which topic?
Options: 1)Athlete, 2)NaturalPlace, 3)Artist, 4)MeanOfTransportation, 5)WrittenWork
A:
4