If A Tree Falls in the Forest

The question is:

If a tree falls in the forest and there is no one there to hear it,
	Will the falling tree make a sound?

If there is a tree, there is a biosphere.
If there is a biosphere, there is air.
If there is air, there are molecules.

And so the tree, when it strikes the ground, 
Will cause a sound wave to ripple through the air.

The answer is: