The correct answer is A) to appeal to his critic's intellect.
King uses this allusion because he wants to appeal to his critic's intellect.
In this part of his "Letter from Birmingham's Jail," Dr. Martin LUther King Jr. uses formal and appropriate figures of language to appeal to his critic's intellect and convey a solid message about his beliefs for a civil resistance with purpose, as the only way the cath the national attention of the American citizens.
The other options of the question were B) to define democratic principles, C) to commemorate a famous leader, and D) to decry the bondage of ancient Greece.