You create a many-to-one relationship between records in table A and table B in the Dataverse database. 
Then, in a model-driven app, you delete the record from table
B. But you still can see the “orphan” records from table A. 
You need to prevent this type of relationship’s behavior that creates “orphan” records. 
Please select the option that would prevent deletion of the parent record that has related child records.

Answer options:

A.Parental
B.Referential Remove Link
C.Custom Delete Cascade All
D.Referential Restrict

Correct Answer: D 
Dataverse defines the two types of relationships between tables: One-to-Many (1:N) and Many-to-Many (N:N). 
A one-to-Many relationship is a Parent-Child relationship, like between a person and multiple email addresses. One person can have multiple email addresses. The person record is related to the multiple records in the Email table from the Person table point. It is a One-to-Many relationship for a person record. For the related email record, this relation is Many-to-One. When you create such a relationship between tables, the Dataverse automatically adds a Lookup column in a child or related table. When you relate two tables in the Many-to-One or One-to-Many relationship, you need to instruct the Dataverse what to do when you delete the records from the parent table. 
There are three advanced options for relationship behavior: Referential, Parental, and Custom. 
Referential type preserves the child records from the actions on the parent records. It has two options: Remove Link and Restrict. 
If you use a Remove Link option, you preserve the child records when a parent record is deleted. 
If you use a Restrict option, you prevent the deletion of the parent records related to child records. 

Option A is incorrect because the Parental type defines the child records` deletion when you delete the parent record. It does not prevent the deletion of the parent record when the related records exist.
Option B is incorrect because the Referential Remove Link type defines the parent record`s deletion without deletion of any related child records. It does not prevent the deletion of the parent record when the related records exist.
Option C is incorrect because Custom Cascade All defines the child records` deletion when you delete the parent record. This behavior is the same as the Parental type. It does not prevent the deletion of the parent record when the related records exist.
For more information about Dataverse table relationship behavior, please visit the below URLs: 

https://docs.microsoft.com/en-us/learn/modules/create-relationship-between-cds-entities/1-relate
https://docs.microsoft.com/en-us/powerapps/maker/data-platform/data-platform-entity-lookup