Final answer:
Class B airspace and within 30 miles of the Class B primary airport require an operable 4096-code transponder and Mode C encoding altimeter.
Step-by-step explanation:
In aviation, the airspace that requires an operable 4096-code transponder and Mode C encoding altimeter is Class B airspace and within 30 miles of the Class B primary airport. This type of airspace is typically found around busy airports and is designed to protect the flow of traffic in and out of the airport.