Which sentence is written correctly?
A.
My oldest relative Arthur Smith has lived in Worchester, the county seat, for more than 100 years.
B.
My oldest relative Arthur Smith has lived in Worchester the county seat for more than 100 years.
C.
My oldest relative, Arthur Smith, has lived in Worchester, the county seat, for more than 100 years.
D.
My oldest relative, Arthur Smith, has lived in Worchester the county seat for more than 100 years.