Based on the clue 'a single residence divided into 3 units', what is the answer?

Based on the clue 'a single one marks the end of a segment a double o...', what is the answer? Based on the clue 'a single one of these is actually an unopened flow...', what is the answer? Based on the clue 'a single rail train line', what is the answer? Based on the clue 'a single red triangular pennant tells boaters that...', what is the answer? Based on the clue 'a single san quentin dweller in solitary', what is the answer? Based on the clue 'a single seat aircraft powered by a small motor', what is the answer? Based on the clue 'a single show of a tv drama', what is the answer? Based on the clue 'a single unit of a general mills cereal or a briti...', what is the answer?