Answer:
I'm as simple as a circle worthless as a leader; but when I follow a group their strength increases tenfold. By myself I'm practically nothing.
I plow and plow but never sow.
I fill a room but take no space.
I carry you down a gentle stream.
I have roots that no one sees and I am taller than trees. Up, up I go, but never do I grow. What am I?
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.
What am I?
Animal
Difficult
Easy
Food
Funny
Kids
Logic