1. Chris __ (fall) off the ladder while he __ (paint) the ceiling.
    1.   Chris fell off the ladder while he was painting the ceiling.
    2.   Chris was falling off the ladder while he painted the ceiling.
  2. You (study) when I (call) you last night?
    1.   Were you were studying when I called you last night?
    2.   Did you study when I was calling you you last night?
  3. They __ (drive) very fast when the policeman __ (stop) them.
    1.   They were driving very fast when the policeman stopped them.
    2.   They drove very fast when the policeman was stopping them.
  4. While I (drive) to work yesterday, I (see) an accident.
    1.   While I was driving to work yesterday, I saw an accident.
    2.   While I drove to work yesterday, I was seeing an accident.
  5. My friends (drop in) for a visit while I (watch) TV last night.
    1.   My friends dropped in for a visit while I was watching TV last night.
    2.   My friends were dropping in for a visit while I watched TV last night.
  6. I (see) Andrea at the party last night. She (wear) a beautiful dress.
    1.   I saw Andrea at the party last night. She was wearing a beautiful dress.
    2.   I was seeing Andrea at the party last night. She wore a beautiful dress.
  7. The children (go) to bed at 9:00 last night. At 10:00, they (sleep).
    1.   The children went to bed at 9:00 last night. At 10:00, they were sleeping.
    2.   The children were going to bed at 9:00 last night. At 10:00, they slept.
  8. Monty (work) in his garage last night when he (hear) a loud noise.
    1.   Monty was working in his garage last night when he heard a loud noise.
    2.   Monty worked in his garage last night when he was hearing a loud noise.
  9. She (break) a plate while she (do) the dishes.
    1.   She was breaking a plate while she did the dishes.
    2.   She broke a plate while she was doing the dishes.
  10. David (meet) his neighbors while he (move) into his new apartment.
    1.   David met his neighbors while he was moving (move) into his new apartment.
    2.   David was meeting his neighbors while he moved (move) into his new apartment.