Final answer:
The British economic system that forced George to ship his indigo crop to Britain, pay high taxes, and sell only to British merchants is known as mercantilism, which was characterized by restrictive trade policies like the Navigation Acts.
Step-by-step explanation:
The British economic system illustrated by George's situation in North America in 1745 is best described as mercantilism. In the mercantilist system, colonies were expected to provide raw materials to the mother country and were restricted from trading with other nations. British policies, including the Navigation Acts, regulated colonial trade to benefit Britain's economy, requiring colonists to ship goods exclusively to Britain, often at less competitive prices, while paying high taxes. This control helped to increase the nation's wealth and expand the empire's economic power, leading to a system where the colonies and their economies were tied to the prosperity of Great Britain.