We __________________ (work/already) on this project for a month before we found a fundamental flaw.
had already been working
The invoice ______________________ (not/arrive/still) by the end of the week so we sent them a strong reminder.
had still not arrived/still had not arrived
I had to have a break. I ______________ (drive) so long
had been driving
Before we parked our car we ___________ (collect) the ticket.
had collected
They got to the beach after they _____________________ (walk)for hours.
had been walking
