Why was the Zimmerman Telegram a contributing factor to the U.S. declaration of war?

1) It showed that Mexico was passing U.S. military secrets to the Germans.
2) It promised Mexico that Germany would help it reclaim territory in the U.S. if Mexico entered the war against the United States.
3) It contained military commands from the Germans to the Mexican government.

The most significant factor was the second reason: the Zimmerman Telegram promised Mexico that Germany would help it reclaim territory in the U.S. if Mexico entered the war against the United States. This directly threatened U.S. national security and was seen as a direct threat to the United States, leading to President Wilson asking Congress to declare war on Germany.

So which answer is the best choice?

The second reason, which states that the Zimmerman Telegram promised Mexico that Germany would help it reclaim territory in the U.S. if Mexico entered the war against the United States, is the most accurate and significant reason for the U.S. declaration of war.