The Zimmermann Telegram added to the U.S.'s reasons for war because it offered a German alliance to Mexico along with a promise to the latter to regain the now-American lands of Texas, Arizona, and New Mexico.
The correct answer is that the iron support structure was visible
When you build something, the structural points such as pillars are usually not easily discernible to the untrained eye because they fit right there with the remaining walls and things like plaster or bricks. However, his Palace was built out of Glass so the iron supporting structures could easily be seen and it looked great.
