I think the correct answer is E .. if it had to be 'A' then the sentence should have read :

Before the storm had destroyed much of the harbor, this town, with its sandy beaches and multiple opportunities for sports, had been one of the most popular resort destinations on the East Coast

Simplifying the sentence ..

"Before A <did something>, C had been <something else>"

This doesn't sound right.. I don't know of an appropriate grammatical explanation.

- pradeep

OA is E

https://www.manhattangmat.com/forums/su-t5236.html

I will go with E as we already has before so time sequence is clear and therfore no need to use past perfect