krndatta
Hello
krndatta,
We hope this finds you well.
To answer your query, both Options D and E alter the intended meaning of the sentence through the phrase "only one of"; the construction of this phrase changes the meaning that "only" conveys, incorrectly implying that the site of the Battle of Princeton was
merely one of eight Revolutionary War battlefields that were still undeveloped; in other words - that the site of the Battle of Princeton was one of eight Revolutionary War battlefields that were still undeveloped,
and it was nothing else.
The intended meaning - as conveyed by the phrase "one of only" in Option A - is that the site of the Battle of Princeton was one of the Revolutionary War battlefields that were still undeveloped, and there were only eight such sites.
We hope this helps.
All the best!
Experts' Global Team