Don't you have to go to B to get to C though? And if you tried to only go to B and stayed on the train you would finish up at C anyway?
I was possibly being unclear. Some transits only go to terminal B, most go to both B and C. Either way you don't get off at B, you stay on until C. Then the transit will return to A, after opening the doors on the right, the recorded message plays, doors on the right close, doors on the left open, transit goes to B then A.