Final answer:
The Spanish monarchy was enriched by receiving a part of the treasures from the conquered Aztec and Incan empires, especially silver, and through economic controls that exploited the colonies. The correct option is C.
Step-by-step explanation:
The defeat of the Aztec and Incan empires enriched the Spanish monarchy primarily because the monarchs received a portion of all treasures taken by the conquistadors. This wealth came not just from gold, but more significantly from silver, notably from regions like Potosí in Peru, which dramatically boosted the Spanish economy.
The encomienda system allowed Spanish encomenderos to profit from the labor of the indigenous population, though officially slavery was forbidden.
Additionally, the Spanish crown enacted policies that ensured that the American colonies were economically beneficial, including monarchical control over lucrative trades and resources and restrictions on colonial trade, compelling the colonies to import finished goods exclusively from Spain and export valuable raw materials, such as silver and gold, which further filled the monarchy's coffers.