A 44-year-old Boston man was pulled from beneath an MBTA Red Line train early Monday after being struck by the train as it entered North Quincy Station, MBTA Transit police said. The man, who was not identified, was lying with his right arm extended onto the track around 12:15 a.m., Transit Police said. The train operator immediately put the train into an emergency stop, but hit the man. Emergency personnel arrived around 12:50 a.m., and the man was freed by the Quincy Fire Department. He was taken to Boston Medical Center for surgery and was listed in critical condition.Sarah N. Mattero can be reached at firstname.lastname@example.org.