I believe the answer is C. Let me know if this helps
The Monroe Doctrine was a United States policy of opposing European colonialism in the Americas beginning in 1823. ... By the end of the 19th century, Monroe's declaration was seen as a defining moment in the foreign policy of the United States and one of its longest-standing tenets.
The fourth of July is the day of freedom for the people of America. In the speech, Douglas comments on the celebration of the day and says that to celebrate such a day is very ironical. He says that the celebration of freedom which the people are celebrating is in reality still under slavery. Hopefully this helps :)
