Answer:
It is a sound of empty, speak and it'll talk back plenty. But all the more you yack, you'll get the same words back.
A hole leading in, a hole leading out, we connect to a cavern that is slimy all throughout. What are we?
Who is it that rows quickly with four oars, but never comes out from under his own roof?
What has six faces and twenty-one eyes?
Voiceless it cries, wingless flutters, toothless bites, mouthless mutters.
I am rarely touched but often held. If you are smart you'll use me well. What am I?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?