I haven't read this in a while, but I'm pretty sure it's C.
Answer: Third person.
Explanation:
The use of the word "they" is a third person indicator.
The first one is his, the second one is whom.
The given sentence above is an example of a sentence. It is a sentence since it has a subject and a predicate, and also, it conveys a complete thought. Clause fragments are those types of clauses that do not have either the subject or predicate and does not convey a complete thought. Hope this answer helps.
