Start at the layer that controls the outcome. The best answer is A. Read-Only access on Case and Issue_c.
Manual record sharing can grant access to individual users, public groups, and roles with subordinates. It is a record-level access mechanism, separate from field-level security and permission set assignment.
The selected answer is stronger because it meets both the functional requirement and the maintainability requirement. In a Salesforce implementation, a solution that only works for one user, one page, or one data sample is not good enough. The correct feature has to behave consistently across the intended profiles, record types, apps, and devices that are part of the design.
The distractors are not equal substitutes. B (Read-Only access on Case and Case Issue_e) is less defensible because it is not the most maintainable declarative control for this design. C (Read-Only access on Case Issue_c) should be rejected because it works at the wrong scope for the object, field, page, automation, or deployment condition in the stem. D (Read-Only access on Issue__c and Case Issue_c) would be fragile here because it could produce an inconsistent result once different users, records, or apps are tested. That is the kind of solution a Salesforce admin can document, migrate, and troubleshoot without creating hidden technical debt.
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