Answer:
Taking into account the specifications, I'd say that the best option to fill in the blanks to achieve a tone and level of standard English appropriate for academic writing is B.
Even though sentence D contains an adverb making the sentence a bit more formal, "aggravating" and "hassle" are informal words. The same happens with A and C. Therefore, I think that "difficult" and "nuisance" are the best choice. This is the case because "difficult" is a neutral word and "nuisance" is the most formal of them all.
