I believe A might be right
(B) A fort was established and many were killed by disease.
After Lewis and Clark's expedition, the people of mandan village were faced by a devastating outbreak of smallpox disease in the year 1837, as much as the epidemic was devastating it played an important role in uniting the surviving people in Mandan and Hidatsa village who later interacted in trade farming and hunting
China's president did not have enough power.
I believe it's C because the emancipation proclamation it declaring that all slaves in slave states to be free.
