Answer:
Commas indicate a natural pause in the sentence.
The correct answer is B, as the winner of that election was the United States first African American president, Barack Obama.
For the first one The institution of slavery contradicted the foundation of the American society because till this day people of color are still being treated horrendously due to their ancestors and their teachings to the newer generation. Also it contradicted it because Americans had their amendments but it didn’t apply to slaves .
I believe the answer is D
