The correct answer is: C. foreign, primary
A primary key is a field that uniquely identifies each record in a table. A foreign key is a field in one table that refers to the primary key of another table. The common field linking the two datasheets is the foreign key in the main datasheet and the primary key in the linked datasheet.
For example, let’s say you have a table of customers and a table of orders. The customer ID field in the orders table would be a foreign key, because it refers to the primary key of the customers table. This is because each order can only be placed by one customer.
The following diagram shows how the two tables are linked:
[Diagram of two tables linked by a foreign key]
The customer ID field in the orders table is the foreign key, and the customer ID field in the customers table is the primary key.
I hope this explanation is helpful! Please let me know if you have any other questions.