For the first question regarding the author's use of vocabulary appropriate for his audience and purpose, the BEST statement is:
B. The author uses Standard American English and metaphors to connect to his audience.
Martin Luther King Jr. employs clear and powerful metaphors, such as "manacles of segregation" and "chains of discrimination," to vividly convey the seriousness of racial inequality. His language is accessible while also maintaining a formal tone suitable for a significant historical speech.
For the second question about the figurative device demonstrated by "manacles of segregation" and "the chains of discrimination," the correct answer is:
B. metaphor.
These phrases are metaphors that signify the oppressive nature of segregation and discrimination by likening them to physical restraints, highlighting the limitations they impose on freedom and equality.