Answer:
What can be as big as an elephant but weighs nothing?
I am an insect and the first part of my name is the name of another insect. What am I?
Everyone in the world needs me. They generously give me but never take me. What am I?
I can be in your body but never on your placemat. I'm always better when I'm fresh, but you'll never see me in the flesh. What am I?
I am the only word that looks the same when spelled upside down.
Of these things - I have two. One for me - and one for you. And when you ask about the price, I simply smile and nod twice.