Riddle #1206

Question: A trail, a union, together tied.
Come across me and you will find,
you cannot change the course I'm on,
without me you cannot travel on.

What am I?

Question: Why did the hen cross the road?

Question: What do you call a sad bird?

Question: What is an astronaut's favorite key on the keyboard?

Question: What is the tallest building in the world?

Question: What tastes better than it smells?