Answer:
I tremble at each breath of air, and yet can heaviest burdens bear. What am I?
I go around in circles, but always straight ahead. Never complain, no matter where I am led. What am I?
Never resting, never still. Moving silently from hill to hill. It does not walk, run or trot. All is cool where it is not. What is it?
What can you catch but not throw?
What is the saddest fruit?
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.