Patricia, a database system manager for a large hotel chain, is setting up a relational database to track customer hotel registrations for each hotel. The table in the database currently includes fields (columns) for First Name, Last Name, Phone, Email, License Plate #, and Check-in Date.
What can Patricia do to make sure that each record (row) in the database is unique?
A. Designate the Phone field as the primary key.
B. Designate the License Plate # field as the primary key.
C. Combine the Email field and the Phone field to use as the primary key.
D. Create an additional Check-in ID field.