Which property must valid a Primary Key possess?

1. A It must be represented by a standard signed 64-bit integer to ensure full compatibility with modern, low-level heap memory management.
2. B It must be mathematically unique across the entire table and cannot contain a NULL state, ensuring every specific row is addressable.
3. C It must be cryptographically encrypted at the hardware level using a rotating public-private key pair before it can be stored on the disk.
4. D It must strictly follow a sequential, monotonic numbering pattern that is automatically incremented by the database's internal ticker.