Answer:
Something wholly unreal, yet seems real to I. Think my friend, tell me where does it lie?
I am the greatest teacher out of them all, but alas in the end I kill my pupils.
What comes once in a minute, twice in a moment, but never in a thousand years?
They're up near the sky, on something very tall. Sometimes they die, only then do they fall.
Brown I am and much admired; many horses have I tried; tire a horse and worry a man; tell me this riddle if you can.
What did the piece of wood say when he saw the screwdriver and screws approaching?