Plz, help me to check my answers...

1. The boys were playing games when it  ___  raining.     (was starting, started, had started)
2. You were watching TV when I ___ for my exam.   (prepared, am preparing, was preparing)
3. We ___ each other for a long time?   (knew, are knowing, have known)
4. We ___ nothing from all the wars from History.   (are learning, have learnt, learnt)
5. I ___ well for the exam.   (prepared, have prepared, had prepared)
6. I ___ well for the exam, yet I failed.   (prepared, have prepared, was prepared)