Final answer:
b) Class C airspace. The primary airport within a TRSA becomes Class D airspace, while the remaining portion of the TRSA usually overlies Class C airspace.
Step-by-step explanation:
The primary airport(s) within the TRSA (Terminal Radar Service Area) become(s) Class D airspace. The remaining portion of the TRSA overlies other controlled airspace, which is normally Class C airspace.
TRSA is a type of airspace designated by the FAA (Federal Aviation Administration) to provide radar services to participating pilots. Class C airspace is generally established around airports with a high volume of IFR (Instrument Flight Rules) operations or passenger-carrying operations.