How do Kafka transactions enable exactly-once semantics for producers, and what are the key steps to use them?

• A. Exactly-once semantics group multiple writes into a single atomic unit. Steps: set transactional.id, call initTransactions, beginTransaction, send records with the same transactional id, then commitTransaction or abortTransaction; also use isolation.level=read_committed on consumers.
• B. Exactly-once semantics are achieved by sending each message with the same key but without transactions.
• C. To enable transactions, you only need to set acks to all; there are no additional steps.
• D. Exactly-once semantics are achieved by increasing replication factor; steps: configure topics accordingly.

Answer: (A)