Answer: I don't know if this is a multiple choice question or not, but I would contend that the speaker mentions Harlem because he can relate to that area of New York where he lives. Harlem is home to him, and he can experience it with all his senses.
Explanation: In this stanza from Langston Hughes's poem "Theme for English B" the speaker seems to be responding to his instructor, who has asked him to go home and write a page, encouraging him to let that page come out of him, since, that way, it will be true. The speaker then wonders if such a task is as simple as it seems. Will his truth, the truth of a young man, be also true for his instructor and for his classmates? And will he be able to identify his truth? As he reveals, he is the only African-American in his class and he lives in Harlem. He does the same things as the rest, yet he is certain he will be seen differently. One thing is true to him: he belongs to Harlem, he feels the city and hears it (this is certainly a reference to the jazz scene that flourished there). He also hears New York (the city must have seem an impressive place to him coming from a Southern town), but his only certainty so far is that Harlem has welcomed him and he feels at ease there.