How should the administrator accomplish this goal?

Cloud Kicks wants users to only be able to choose Opportunity stage closed won if the Lead source has been selected.

How should the administrator accomplish this goal?
A . Make Lead Source a dependent picklist to the Opportunity stage field.
B . Configure a validation rule requiring Lead Source when the stage is set to closed won.
C . Change the Opportunity stage field to read only on the page layout.
D . Modify the Opportunity stage a dependent picklist to the Lead source field.

Answer: B

Explanation:

Validation rules allow you to enforce data quality by preventing users from saving records that do not meet certain criteria.

Reference: https://help.salesforce.com/s/articleView?id=sf.validation_rules.htm&type=5