Read this line from "Empire State Building." It's lonely up here without my big twin brothers,

the World Trade Center Towers.

Which fact is most important for readers to know in order to understand the significance of this line?

The World Trade Center Towers were important office buildings.
The World Trade Center Towers were extremely tall.
The World Trade Center Towers fell on September 11, 2001.
The World Trade Center Towers were built in the early 1970s.