    Sentence |: _- What science fiction writer  introduced ‘the Doctor .Who — episodes  fora period of time?    Sentence 2: From 1979: to 1981,   Tvo “ airings: were  bookended by science-fiction writer Judith  Merril who» would ~ introduce — the  episode: and then, after the episode  concluded, “try to place it in. an  educational context in keeping with TVO's:  ‘status as on.educational channel.