Option C (IAM) is correct because IAM logs are audit logs that cannot be turned off but generate minimal data compared to other types. Options A (VPC Flow logs) and D (Load Balancer) are incorrect as they can generate a large volume of logs, though Load Balancer logging can be disabled. Option B (Data Access logs) is also incorrect because, although they're off by default due to high log generation, they can still be a significant source when enabled. References: Google Cloud Load Balancing, Google Cloud Logging, Google Cloud Audit Logs.