You need to implement a computed column that references a lookup table by using an INNER JOIN against another table

You use Microsoft SQL Server 2012 to develop a database application.
You need to implement a computed column that references a lookup table by using an INNER JOIN
against another table.
What should you do?

A.
Reference a user-defined function within the computed column.

B.
Create a BEFORE trigger that maintains the state of the computed column.

C.
Add a default constraint to the computed column that implements hard-coded values.

D.
Add a default constraint to the computed column that implements hard-coded CASE statements.