Option B presents the sentence that supports the answer to part A. This sentence presents that: "When the architects of our republic wrote the magnificent words of the Constitution and the Declaration of Independence, they were signing a promissory note"
The above question is related to the "I Have a Dream" speech given by Martin Luther King. In this, he shows the reasons that make African Americans fight for equality. Furthermore, he shows that this struggle is not illegal, as the country's constitution allows rights for all Americans.
Part A asks what is the purpose of the fourth paragraph of this speech and we can say that the purpose of this paragraph is to show that African Americans should not and will not stop fighting for their rights because the constitution allows them to do so.
More information about Martin Luther King at the link:
https://brainly.com/question/878248