Exam Certified Sharing and Visibility Architect topic 1 question 81 discussion

Improvement on my first response: Sharing sets are specifically designed for community users. Account Contact Relationships (ACR) allow you to define relationships between contacts and multiple accounts This maintains proper data security while allowing flexible access B. is not it, because sharing rules are primarily for internal users and they can't leverage the Account Contact Relationship model. C. is not it, because it's an unnecessarily complex solution that uses custom code when there are declarative tools that can do the same thing.

This is a best answer question, so A is the choice. A, B, C provide the needed functionality. Sharing Sets are specifically for Customer and Partner communities (external users) and use profiles instead of of roles and public groups. Sharing rules can be used for role based licenses only (Customer Community Plus, Partner User), so this is a viable option. Sharing rules are generally used for broader sharing criteria and may not be as suitable for this specific scenario and maintenance issues will arise.