What Bluetooth pairing mode is "Numeric Comparison" and how does it protect against MITM attacks compared to "Just Works"?

• A.Numeric Comparison exists for Bluetooth Classic, and low-energy pairing falls back to Just Works whatever the peripheral advertises; the protection is therefore unavailable on a wearable or a sensor, because the low-energy stack omits the display negotiation the model needs. A user pairing a fitness band gets no confirmation prompt.
• B.Numeric Comparison validates a manufacturer certificate presented by the peripheral, and the handset checks it against a root the Bluetooth SIG publishes; the protection follows from that chain, because a man in the middle has no certificate the root will vouch for. Just Works skips the certificate exchange, and the two models differ in provenance rather than in user involvement.
• C.Numeric Comparison displays a 6-digit number on both devices and requires the user to confirm they match; this proves both devices are communicating directly and prevents a MITM from inserting a different key exchange, unlike Just Works which has no MITM protection.