Final answer:
The primary video service offered by cable systems is the Basic service, which includes local broadcast stations and may feature a few extra channels as mandated by the FCC.
Step-by-step explanation:
The primary video service offered by a cable system is the Basic service. Basic service includes a selection of local broadcast stations and possibly a few additional channels. This foundational package is a requirement set forth by the Federal Communications Commission (FCC), which ensures that certain essential local broadcast programming is accessible via cable systems. Cable providers can then offer additional tiers of service, such as Expanded service, which includes more channels that are not available in the basic tier, and Premium services or Premium commercial-free services, which typically include specialized content like movies and original series that are ad-free.