Final answer:
The correct answer is O Zimmermann Telegram. It was a message sent by Germany during World War I to Mexico, proposing a military alliance.
Step-by-step explanation:
The correct answer is O Zimmermann Telegram. The Zimmermann Telegram was a message sent by Germany to Mexico during World War I, proposing a military alliance between the two countries. It was intercepted and decoded by the British, which contributed to the United States' decision to declare war on Germany.
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