The correct answer is B. Occurred in Philadelphia in 1787
Explanation:
In grammar, a fragment refers to a set of words that go together but are not sentences because they do not have a complete meaning, a subject (the entity that carries out the action) or a verb (action of the sentence). Because of this, fragments can usually be corrected or made into sentences by adding a subject, a verb or other type of words to make it complete. Also, the type of information that needs to be added depends on the information that is already included in the fragment. This means a fragment that could be corrected by only adding a subject is a fragment that contains a verb and some information about it that works as a complement but lacks a subject. Considering this, the fragment that you could correct by adding only a subject is "occurred in Philadelphia in 1787" because this fragment contains a verb "occurred" and a complement "in Philadelphia in 1787", which means by adding only a subject such as "the convention" or "the accident" the fragment would be corrected into a complete sentence.
