Answer:
What has roots that nobody sees, and is taller than trees. Up, up it goes, and yet it never grows.
What binds two people yet touches only one?
Crooked as a rainbow, and slick as a plate, Ten thousand horses can't pull it straight.
We are all around, yet to us you are half blind. Sunlight makes us invisible, and difficult to find.
What bird can lift the heaviest weight?
People take me on walks and I run and have fun. What am I?