the phrase "your new-caught sullen peoples, /half devil and half child" is an example of what belief that europeans used to justify imperialism?

Scientific racism

Explanation: The line is from “The White Man’s Burden.” Europeans considered themselves superior to other races, and thought it was their mission to “civilize” them. This is how they justified imperialism, and the invasion and exploitation of other nations.

b.   jim crow laws were enacted in northern states.

powers  are  denied  to the  national governmentin three distinct ways: some  powers, such as the  power  to levy duties on exports or prohibit the freedom of religion, speech, press, or assembly, are expressly  denied  to the  national government  in the  constitution.