How can an administrator meet this requirement?

The VP of Finance wants to ensure that once an opportunity is closed, it cannot be modified by any user.

How can an administrator meet this requirement?
A . Create a workflow field update to update the IsClosed field to True if a closed opportunity is modified.
B . Set the Do Not Modify Closed Opportunity permission for all profiles.
C . Set all fields to Read-Only on the standard Closed Opportunity page layout.
D . Create an opportunity validation rule with the formula: PRIORVALUE( IsClosed ) = True.

View Answer

Answer: D