Choose the correct tense

1. Ann felt cold because she [had forgotten|had been forgetting] to take her coat.
2. How long [did Aron climbed|had Aron been climbing] before the accident happened?
3. Peter was upset because he [had been seeing|had seen] a horrible car crash.
4. They [walked|had been walking] in the forest for hours before they realised they were lost.
5. Tom [had been waiting|waited] for two hours when the rescue helicopter finally arrived.