Final answer:
The Spanish built missions in valleys for protection and sustainability. The Castillo de San Marcos was constructed to defend against other European powers. A major driving force in Spanish exploration was the desire to spread Christianity.
Step-by-step explanation:
Location Choices for Spanish Missions
The Spanish chose locations for their missions with strategic purposes in mind. The correct choice is D. They built missions in the valleys for more protection. Valleys offered a natural barrier against potential enemy attacks and were often more fertile areas for agriculture, which was essential for the sustenance of mission populations.
Castillo de San Marcos
The Castillo de San Marcos was built by the Spanish largely B. to defend against imperial challengers. Located in St. Augustine, Florida, it was part of the Spanish efforts to protect their interests and thwart the advances of other European powers, such as the English and the French, in the region.
Motivation Behind Spanish Exploration
Alongside the thirst for wealth, a. the desire to spread Christianity and counter the influence of Islam was a key motivating force for both Spain and Portugal in exploring new lands. This is evident in the existence of the mission system and the efforts of the clergy to convert and educate the indigenous populations they encountered.