Northerner used the term slave power to criticize white southerners who practiced obsessive political power.
Plessy v. Ferguson set forth the doctrine of "separate but equal" which enabled institutionalized segregation as long as things were "equal"
However, the Court did not define what equal really meant.
So, you might see a bathroom for African-Americans that was a hole in the ground while the whites only bathroom was pristine and modern.
Answer: D is right. But there are also many other reasons.
Explanation: League of Nations was formed by Allied powers (from the WW I) so consequently it was viewed as "League of Victors". Moreover USA did not join, may other states did not join and later on League of Nations was unable the prevent outbreak of WW II.
Back then, the answer would be A. But, if this was a MODERN question, the answer would be D.
I believe that the president sends the laws to the states for approval.