I believe it is A. religious wars and conflicts related to the beliefs of the two largest faiths.
Biological warfare was effective against the Inca because there immune system's were not used to that type of diseases that Europeans brought over. There are very susceptible to disease and were wiped out quickly
Explanation:
to cross the Continental Divide
In the mid-1830s Narcissa Whitman and Eliza Spalding became the first white women to cross the Continental Divide when they accompanied their husbands—Marcus Whitman and Henry Harmon Spalding—on a Congregationalist mission in the Northwest.
