D. I can tell that the author is speaking to motivate his audience.
Explanation:
Answer choice "D," is correct because Martin Luther King Jr. is telling everyone in their whole community/society of the racial injustice that he and his people have had to deal with all those years. He is talking about how the Negro want their own freedom, that should be rightfully theirs. He discusses the horrors they've had to face, the discrimination against them by everyone around them. By making this speech, Dr. King was hoping to persuade/convince the audience, possibly higher-ups, to change their society and give them back their freedom.
