Which Service Bus metric should you monitor to detect messages accumulating faster than they are being processed?

1. ✓ A Active message count (queue depth) (correct answer)
2. B Dead-letter message count
3. C Server errors metric
4. D Connection count

Shortcut: Active message count (queue depth) indicates how many messages are awaiting processing. A rising count signals that consumers are slower than producers — scale consumers or investigate processing bottlenecks.