How should a developer make sure that a child record on a custom object, with a lookup to the Account object, has the same sharing access as its associated account?

How should a developer make sure that a child record on a custom object, with a lookup to the Account object, has the same sharing access as its associated account?
A . Create a Sharing Rule comparing the custom object owner to the account owner.
B . Create a validation rule on the custom object comparing the record owners on both records.
C . Include the sharing related list on the custom object page layout.
D . Ensure that the relationship between the objects is Master-Detail.

Answer: D