An alliance made to defend one another if attacked by any other country; US, England, France, Canada, Western European countries.

• A. NATO
• B. IMF
• C. United Nations
• D. European Union

Answer: (A)

Collective defense under a treaty is what this describes: countries pledge to defend one another if attacked. NATO fits this description. It was formed in 1949 by the United States, Canada, and Western European countries to deter aggression during the Cold War. The defining feature is that an armed attack against one member is treated as an attack against all, and member states commit to coming to one another’s aid. That makes NATO the best answer. Other options don’t fit as neatly: the IMF handles monetary stability, not defense; the United Nations is a broad international body focused on peace and security rather than a formal mutual defense pledge; the European Union is a political-economic union, not a treaty-based mutual defense alliance in the same way NATO is.