For now you have decided to create at least two tables for the Philosophers Database described in the question above. You create Table Eras and Table Philosophers and Works. What field must you add to Table Era to make sure that each record (entity) in the table is uniquely identified? O A. A foreign key in Table Eras. I would call it Era_ID and make sure that every entry in Era_ID is unique. OB. A foreign key in Philosophers and Works. I would call it Era_ID and make sure that every entry in Era_ID in Philosophers and Works is unique. OC. A primary key in Table Philosophers and Works. I would call it Phil_ID and make sure that every entry in Phil_ID is unique. D. A primary key in Table Eras. I would call it Era_ID and make sure that every entry in Era_ID is unique