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