A legal hold is the correct answer because the organization is preserving potentially relevant evidence after a suspected breach involving sensitive client information. In incident response and governance, legal hold prevents deletion, alteration, or routine retention-policy destruction of data that may be required for litigation, regulatory investigation, discovery, or internal investigation. Logs, server images, and email communications are exactly the kinds of records that may become evidence. Chain of custody is related but narrower: it documents who handled evidence, when, and how integrity was maintained. Root cause analysis happens later to determine why the breach occurred. Containment focuses on stopping spread or limiting damage. Here, the key action is preservation of records.