You need to implement a computed column that references…

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.

Explanation:
A common way to define a computed column is by using a user-defined function (UDF) to encapsulate the
calculation logic.
https://blogs.msdn.microsoft.com/sqlcat/2011/11/28/a-computed-column-defined-with-a-userdefined-function-might-impact-query-performance/