Answer: the policy or ethos of using power and influence to control another nation or people that underlies colonialism.
Explanation:
A) A fort was established and many were killed by diseases
Lewis and Clark's expedition was not positive to the native of Mandan village the most devastating epidemic was the smallpox outbreak in the year 1837 killing a lot of people. The epidemic played an important factor in uniting the surviving Mandans and Hidatsa who later engaged in trade, farming and hunting.
Black holes themselves can not be seen, nor do they leave trails (since emptiness does not have to be caused by a black hole), but there is evidence for black holes: scientists can see the effects of their gravity on nearby stars. The answer is B.
The first one I hope I helped
