The correct answer is D. Trade bread for wheat
Step-by-step explanation:
A barter system refers to a basic trade system in which one product or service is exchanged or traded for another. This differs from other systems because there is no money involved. Additionally, in a barter system, individuals trade products they produce to obtain those they cannot produce.
This implies, in the case of a baker it is likely he trades bread for wheat because in a barter system there is no money involved, and also the baker can trade bread for wheat as he needs wheat to produce bread, and bread is a product he produces in large amounts.