Which Service Bus client library method enables efficient message processing across multiple concurrent processors?

1. ✓ A ServiceBusProcessor with MaxConcurrentCalls (correct answer)
2. B Sequential ReceiveMessageAsync in a loop
3. C ServiceBusSender batch sends
4. D ServiceBusSessionProcessor for all queues

Shortcut: ServiceBusProcessor with MaxConcurrentCalls processes messages concurrently. It handles lock renewal, error handling, and auto-complete/abandon, simplifying high-throughput consumers.