Answer:
The more of it there is, the less you see.
Who eats a lot of iron without getting sick?
They belong to me; they belong to you; They can make you feel happy or make you feel blue; They never end until the day you do.
Mountains will crumble and temples will fall. And no man can survive its endless call.
Runs smoother than any rhyme, loves to fall but cannot climb.
As round as an apple. As deep as a cup. All the king's horses can't pull it up.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?