Prepositional phrases can be made up of a million different words, but they tend to ... This whole phrase, in turn, takes on a modifying role, acting as an adjective or an ... The professor can sit on the desk (when he's being informal) or behind the ... It doesn't take a grammarian to spot a sentence-ending preposition
I believe the answer would be "is being torn down soon".
Explanation:
It's been years since I've learned about prepositional phrases (I did so in 7th grade), but from what I understand prepositional phrases complete the sentence. So, "is being torn down soon" completes the sentence. Without that phrase, the sentence would not make sense and would instead be a fragment.
"poetic description" is the only real option from the list that is not common in expository writing, although careful descriptions can indeed be used as long as the point remains clear and forceful.