Answer:
Declare war on Germany, is the right answer.
Step-by-step explanation:
The Foreign Office of Germany in January 1917 issues secret diplomatic information aimed to form a militant alliance between Germany and Mexico, this communication is known as the Zimmermann Telegram. According to the telegram, Mexico would regain the regions Arizona, New Mexico and Texas, if the U.S. enters the First World War against Germany. The telegram convinced the Congress of the United States to Declare war on Germany.