C. spain backs more voyages
the continuine search for asia

Explanation:Spanish claims to the West Coast of North America date to the papal bull of 1493, and the Treaty of Tordesillas. In 1513, this claim was reinforced by Spanish explorer Vasco Núñez de Balboa, the first European to sight the Pacific Ocean, when he claimed all lands adjoining this ocean for the Spanish Crown. Spain only started to colonize the claimed territory north of present-day Mexico in the 18th century, when it settled the northern coast of Las Californias (California).

Starting in the mid-18th century, Spain's claim began to be challenged in the form of British and Russian fur trading and colonization. King Charles III of Spain and his successors sent a number of expeditions from New Spain to present-day Canada and Alaska between 1774 and 1793, to counter the threat of Russian and British colonizers and to strengthen the Spanish claim. During this period of history it was important for a nation's claims to be backed up by exploration and the

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porter is writing economic history because he is focusing on the cost of developing vaccines.