Fill in the gaps with the correct options from the box

• couldn't have known
• needn't have been
• must have left
• could have driven
• might have forgotten
• ought to have called

1. Nobody told her anything about the argument. She
   [ ] about it.
2. We arrived too early. We
   [ ] in such a hurry.
3. She
   [ ] the office because her coat and bag aren't here.
4. I
   [ ] to work, but the weather was so nice that I decided to walk.
5. It's possible that I
   [ ] to tell Joe about the meeting.
6. You
   [ ] her on her birthday. She never forgets to call you.