In the middle of our lunch there was a knock at the door.

When _____________________________________

• A. 
  we were having lunch, there was a knock at the door.
• B. 
  we knocked at the door, we were having lunch.
• C. 
  we had just finished lunch, there was a knock at the door.
• D. 
  our lunch were in the middle there Was a knock at the door.