Answer:
A. So in the best interest of my studies, my music, and my social life, I respectfully request that you let me have my own room.
Step-by-step explanation:
The best way to revise sentences 27 and 28 is: So in the best interest of my studies, my music, and my social life, I respectfully request that you let me have my own room.
In fact, sentence 27 can't even be called a sentence. A sentence must contain a subject and predicate and express a complete thought. Sentence 27 doesn't have any of those elements. However, when we connect it to sentence 28 (which has truly is a sentence), we get one grammatically correct expanded sentence.
Option B is the second best option, but it sounds more awkward than option A.
Option C is incorrect because neither of the sentences is complete, and we already explained why option D isn't correct either.
That leaves us with option A as the correct one.