An iPhone user receives an 'Unknown Accessory Detected' alert on their phone after leaving an airport lounge. The alert says an item has been traveling with them. What Apple feature generates this alert and what privacy problem does it address?

• A.iOS Bluetooth threat detection: the subsystem watches for a low-energy peripheral advertising an unrecognized service UUID, and it warns the owner when the same beacon reappears across separate locations
• B.Find My's Unknown Tracker Alerts: it detects AirTags or Find My-enabled accessories that have been separated from their owner's device and are moving with a non-owner, addressing the risk of covert location tracking using AirTags
• C.Lost Mode synchronization: the alert fires when a device the owner marked missing comes within Bluetooth range, and the finder's handset relays the position to iCloud
• D.NFC proximity reading: the alert appears when the reader detects a tag embedded in luggage, and the tag belongs to another traveler