On the gift card object, what type of field should be created to support this requirement?

Cloud Kicks (CK) wants to set up a custom child object to track gift cards issued to a customer. A key requirement is to track the total number of gift cards opened and gift cards issued on an Account. CK wants to permanently ensure the gift cards are unable to be moved across any other Account once it is created.

On the gift card object, what type of field should be created to support this requirement?
A . Master-detail relationship
B. Roll-up summary
C. Formula
D. Lookup relationship

Answer: A