The possible extension of the MBTA Silver Line into Chelsea will be the focus of a second public meeting this Wednesday from 6 to 8 p.m. in the City Council chambers in City Hall. The state Department of Transportation is exploring extending the bus rapid transit service from South Station and the Seaport District to connect with the Blue Line at Airport Station in East Boston and to stops in Chelsea. As part of that effort, the state agency is working with Chelsea officials to review two possible routes into Chelsea. One would follow Central Avenue into Bellingham Square, while the other would go along an abandoned rail line to the commuter rail station and possibly to Mystic Mall. Extending the line into Chelsea would connect the city with key locations in Boston such as the World Trade Center, the federal courthouse, and South Station. “This is a terrific way to improve our connection to places of importance and job growth, and to encourage both for ourselves,” Chelsea City Manager Jay Ash said in a statement.