The answer is B. "America should make immediate changes to ensure equality for all people".
By using the repetition of "Now is the time", King was attempting to inspire people to fight for equality as soon as possible.
King also used the sentence: "This is no time to engage in the luxury of cooling off or to take the tranquilizing drug of gradualism." By using this sentence, King is stating that now is not the time to wait for equality and freedom to be granted. Instead, they should fight for it currently and not wait, as past generations did.
By using both of these techniques, King is inspiring people, specifically Americans, to immediately begin working towards freedom and equality for all.
Hope this helps! :)