Read the excerpt from Dr. Martin Luther King Jr's "I Have a Dream" speech.
[1] I am happy to join with you today in what will go down in history as the greatest demonstration for freedom in the history of our nation.
[2] Five score years ago, a great American, in whose symbolic shadow we stand today, signed the Emancipation Proclamation. This momentous decree
came as a great beacon light of hope to millions of Negro slaves who had been seared in the flames of withering injustice. It came as a joyous daybreak to
end the long night of their captivity.
(3) But one hundred years later, the Negro still is not free; one hundred years later, the life of the Negro is still sadly crippled by the manacles of
segregation and the chains of discrimination; one hundred years later, the Negro lives on a lonely island of poverty in the midst of a vast ocean of material
prosperity; one hundred years later, the Negro is still languished in the comers of American society and finds himself in exile in his own land.
Which phrase from the text provides the best context clue to determine the meaning of "manacles" in paragraph 3?

A. One hundred years later
B. Chains of discrimination
C. Lonely island of poverty
D. Vast ocean of material prosperity