Which article of the NATO treaty stipulates the principle of collective defense?
A. Article 3
B. Article 4
C. Article 5
D. Article 6
A. Article 3
B. Article 4
C. Article 5
D. Article 6
A. Economic cooperation
B. Political integration
C. Collective defense
D. Scientific research
A. Sweden & France
B. Sweden & Turkey
C. Sweden & Finland
D. Sweden & Norway