The correct answer is B. The Zimmerman note.
Explanation
Zimmermann note was a telegram sent by the foreign affairs minister of the German Empire, Arthur Zimmermann (hence the name of the event) to the German ambassador in Mexico on January 16, 1917. This telegram was intended to instruct the German ambassador to approach the Mexican government offering financial and arms support to alliance against the United States and in this way Mexico could recover lost territories in Texas, Arizona and New Mexico. However, this telegram was intercepted by the British spy, that then sent to the government of the United States. This event led the United States to declare war on Germany during World War I. So, the correct answer is B. The Zimmerman note.
