Why Validation Rule?
Validation rules are efficient for enforcing field-level conditions without requiring Apex or Flow.
A formula can check if the user's profile is not "Sales Manager" and if theLost Reasonfield is blank whenStatusis set to "Closed Lost".
Why Not Other Options?
A: Triggers are more complex and unnecessary for this simple validation.
C: Record-triggered flows are less efficient for field validations compared to validation rules.
D: Approval processes do not handle this type of field-level restriction.
References:Validation Rule Documentation:https://help.salesforce.com/s/articleView?id=sf.
fields_about_field_validation.htm