In Dual Labor Market Theories, the Primary Labor Market Is

In dual labor market theories, the primary labor market is limited to a certain sector of the private economy. What is another name for this market and an illustrative industry or company?

A) a core sector such as BNSF Railway
B) a core economy such as steel
C) a monopoly economy, such as the electric power grid corporations
D) a core sector, such as retail (e.g. Federated Department Stores)