AFFIMATIVE(1) NEGATIVE (2) INTEROGATIVE (3)
1 - You had been waiting there for more than two hours when she finally arrived.
2 - You had not been waiting there for more than two hours when she finally arrived.
3 - Had you been waiting there for more than two hours when she finally arrived?
1 - They had been talking for over an hour before Sandy arrived.
2 - They had not been talking for over an hour before Sandy arrived.
3 - Had they been talking for over an hour before Sandy arrived?
1 - John had been teaching at the university for more than a year before he left for Asia.
2 - John had not been teaching at the university for more than a year before he left for Asia.
3 - Had John been teaching at the university for more than a year before he left for Asia?