I ARRIVED AT WORK. THE ASSISTANT KNOCKED AT THE DOOR.A, I HAD TO A...

25. I arrived at work. The assistant knocked at the door.A, I had to arrive at work as The assistant knocked at the door.B. Had The assistant knocked at the door, I would have arrived at work.C. No sooner had I arrived at work than the assistant knocked at the door.D. I hardly knew The assistant knocked at the door as I just arrived at work.