Correct! The answer here is b.
This kind of situation actually can create some amusing images. The rule is that an introductory phrase must modify the subject of a sentence. That being the case, if the subject is Larrison Hall then the image is that this huge building is actually driving down Newman Springs Road. The students are the ones "coming in" not Larrison Hall. Only b and c offer that choice, and c is too wordy and awkward.