Answer:
Answer is Option C: If the United States entered the war, Germany would enter into a military alliance with Mexico.
Step-by-step explanation:
The "Zimmermann Telegram" was a like a text communication that was issued from the Germany (Foreign Secretary) to Mexico which suggested a military alliance between Germany and Mexico, in case United States enters the World War I. It also agreed that Germany would give considerable financial support to Mexico in case it agrees to be a German ally.
This was intercepted from by US. Other Options which say that Germany would target US coaling stations or US ambassador would be arrested are incorrect. Even the statement about German U boats is incorrect. As this was not intercepted from Zimmermann Telegram.