Another name for a dependent clause is subordinate clause. Option D is correct.
A subordinate clause or dependent clause will begin with a subordinate conjunction or a relative pronoun and will contain both a subject and a verb. This combination of words will not create a complete sentence. It will instead make a reader want additional information to finish the thought. A sependent clause cannot stand alone.
In “Letter from Birmingham Jail” Martin Luther King Jr. structures his ideas strategically as he uses symbolism and rhetorical questions to persuade his readers to help put an end to segregation.