The Preamble. The government does not get its power from a king or Congress, it receives all of its power from the people it serves. The concept of popular sovereignty is reflected in the United States today because people have the right to vote.
The answer to your question is A. American soldiers who liberated extermination camps were unaware of how horrible the Holocaust had been if you are talking about in reference to the article of Barack Obama in 2013. Hope this helps!