
Verbe régulier : happen -  happened - happened
Traduction française : arriver - se passer 
| Forme simple | Forme en V-ing | 
| - - it could happen - - - | - - it could be happening - - - | 
| Perfect | Perfect en V-ing | 
| - - it could have happened - - - | - - it could have been happening - - - | 
| Forme simple | Forme en V-ing | 
| - - it could not happen - - - | - - it could not be happening - - - | 
| Perfect | Perfect en V-ing | 
| - - it could not have happened - - - | - - it could not have been happening - - - | 
| Forme simple | Forme en V-ing | 
| - - could it happen? - - - | - - could it be happening? - - - | 
| Perfect | Perfect en V-ing | 
| - - could it have happened? - - - | - - could it have been happening? - - - | 
| Forme simple | Forme en V-ing | 
| - - could it not happen? - - - | - - could it not be happening? - - - | 
| Perfect | Perfect en V-ing | 
| - - could it not have happened? - - - | - - could it not have been happening? - - - |