The correct answer is: C. Made up of two or more fields to uniquely identify records.
A composite key is a primary key that is made up of two or more fields. It is used to uniquely identify records in a table. For example, a table of employees might have a composite key made up of the employee’s first name and last name. This would ensure that each employee is only represented once in the table.
Option A is incorrect because a composite key is not required when a table does not have any unique fields in it. In this case, a single-field primary key can be used.
Option B is incorrect because the primary key with AutoNumber as the field type is not necessarily a composite key. It can be a single-field primary key.
Option D is incorrect because a foreign key is a field or group of fields that refers to the primary key of another table. It is not used to uniquely identify records.