Ответ:

  1. saw — Second conditional: “If I saw a snake, I’d be terrified.”
  2. would you do — “What would you do if a large dog attacked you?”
  3. wouldn’t buy — “I wouldn’t buy that bike if I were you.”
  4. have lived — Present perfect with “since”.
  5. for — “For a long time” describes a period.
  6. How long — asks about duration.
  7. have been — “I have been married for 15 years.”
  8. did — “When did Queen Victoria die?”
  9. was invented — passive voice, past simple.
  10. written — “The first book in the series was written ten years ago.”
  11. by — names the agent in a passive sentence.
  12. used to — describes a past state or habit.
  13. didn’t use to — after “didn’t”, use the base form.
  14. buy — “might” is followed by the base form.
  15. might not — “She might not come tonight.”