Universal Containers manages leads in a Lead qualification queue where Sales reps can accept ownership...

The correct validation rule is:

AND(

ISNEW(),

ISBLANK(Lead.Owner:User.Id)

)

This rule prevents a new Campaign Member from being created when the related Lead does not have a User as owner. Leads can be owned by either a user or a queue, and Salesforce queues can own Lead records.

Salesforce validation rules block a save when the formula evaluates to True. The ISNEW() function checks whether the record is being created, and ISBLANK() checks whether the Lead owner’s User Id is empty.

For owner fields in cross-object formulas, Salesforce requires being explicit about the owner type, such as Owner:User or Owner:Queue .

Why not others:

A is wrong because Lead.Owner.Id is normally populated whether the owner is a user or queue.

B and D focus on queue ownership, but the best exam answer checks that the Lead has an actual User owner when the Campaign Member is created.