The answer is b) the Zimmerman note- a note to Mexico saying that if the u.s. Declares war on Germany then Mexico should declare war on the u.s.
B however, before it could come to fruition, british intelligence intercepted the telegram and decyphered it
The Zimmermann Telegram was a secret message from Germany to Mexico proposing an alliance against the U.S. in 1917. This communication promised Mexico the return of territories lost in the Mexican-American War. Its interception and revelation significantly influenced the U.S. decision to enter World War I against Germany.
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