I would say Liberalism, in my opinion.
MLA format is the best and what i had to use for everything in my English 11
From the Birmingham jail, where he was imprisoned as a participant in nonviolent demonstrations against segregation, Dr. Martin Luther King, Jr., wrote in longhand the letter which follows. It was his response to a public statement of concern and caution issued by eight white religious leaders of the South.
If the word to be underlined was populace, the answer would be D. The inhabitants of a city or region. If the word to be underlined was officials, the answer could be any/all of the above.