Which BART line connects Fremont, Union City, and Oakland?

The Green Line is the correct choice as it specifically serves the areas of Fremont, Union City, and Oakland in the BART system. This line plays a crucial role in connecting commuters traveling between these cities, facilitating transit for those who work or study in various locations throughout the Bay Area. The Green Line extends from the southern area of Fremont, through Union City, and into the central hubs of Oakland, making it an essential route for local and regional travel.

In the context of the other lines, they serve different areas or connections within the BART system. Understanding the specific routes and the areas they cover helps in navigating the transit system effectively. The Green Line's designated service regions not only support daily commuters but also contribute to the overall accessibility and integration of transit within the broader Bay Area transportation network.