1. How long have we been discussing this matter?
Who has been discussing?
What we have been doing for two hours?
2. How long had your friend serving in the army?
What had he been doing for ten years?
What did he do before the army?
When did he go at the factory?
3. How long has the film been running?
What has been running for a month?
4. What had we been doing for three hours?
Who had been showing?
What did the new engineer say?
When did the new engineer say?