Final answer:
A Lookup Relationship should be used to relate an account to a region in Salesforce.
Step-by-step explanation:
To relate an account to a region in Salesforce, a developer should use a Lookup Relationship with the Region object. A Lookup Relationship is used when there is a simple one-to-one or one-to-many relationship between two objects. In this case, each account can be related to only one region, making it a one-to-one relationship. The Lookup Relationship is optional, meaning an account can exist without being related to a region.