Final answer:
The correct answer to this database question is 'D) Non-redundant,' meaning no attribute in the key can be deleted without losing the ability to uniquely identify a record in a table.
Step-by-step explanation:
The key should be non-redundant; that is, no attribute in the key can be deleted without destroying its unique identification.
In the context of databases, normalization is a process of organizing data to reduce redundancy and improve data integrity. A primary key is an important aspect of database normalization, ensuring that each record within a table can be uniquely identified.
The term non-redundant implies that every part of the key is necessary for maintaining the database's integrity. If the key were redundant, it would contain unnecessary attributes, which contradicts the principles of efficient database design. Thus, for a key to serve its purpose effectively, it must be pared down to the minimal set of attributes required for unique identification, making 'D) Non-redundant' the correct answer.