Task: Text Categorization
Input (English): Context: The NAVO RK-4/220 was a Dutch aircraft originally designed for unofficial crowd observation but which was completed as an airliner. Only one was built; it flew but was never certified.
Question: The document can be classified to which topic? 
Options: 1)Building, 2)Album, 3)Athlete, 4)MeanOfTransportation, 5)Plant
Output (English): 4