Final answer:
Martin Luther King Jr. uses the technique of repetition to emphasize his points in this passage.
Step-by-step explanation:
In this passage, Martin Luther King Jr. most clearly uses the technique of repetition to emphasize his points. He repeats certain words and phrases such as 'I refuse to accept' and 'man's present nature' to drive home his message and make it more impactful. By repeating these key phrases, he makes his stance and beliefs about the ambiguities of history and the moral capability of individuals more memorable and forceful.