Option C is correct because Data Access Logs provide information about users accessing data. Enabling these logs for the audited buckets allows tracking and monitoring of data access on Cloud Storage. The Log viewer can then be used to query and compile the necessary information for the auditor.

Option A is incorrect because Cloud Monitoring does not track data access; it focuses on performance and health metrics.

Option B is incorrect because Admin Activity Audit Logs do not contain data access information; they record administrative actions.

Option D is incorrect for the same reason as Option B; Admin activity logs do not provide user-specific data access details.