Unlike traditional message queues, Kafka acts as a storage system. What determines how long a record stays in the cluster?

1. A The record is deleted as soon as the first consumer in the group reads it.
2. B Records are kept until the whole cluster is restarted.
3. C A configurable retention policy (based on time, e.g., 7 days, or size, e.g., 100GB), regardless of consumer status.
4. D Records are only kept if they are marked as 'Critical' by the producer.