If Two People Exchange an Apple,they Each Still Have Just

If two people exchange an apple,they each still have just one apple,but if they exchange ideas,they now each have two ideas.This is an illustration of

A) the importance of natural resources.
B) the principle of specialization of labour.
C) the difference between information and all the other factors of production.
D) the importance of profit in market economies.
E) all of these.