
Regular verb: happen - happened - happened
| Simple form | V-ing form | 
| - - it ought to happen - - - | - - it ought to be happening - - - | 
| Perfect | V-ing perfect | 
| - - it ought to have happened - - - | - - it ought to have been happening - - - | 
| Simple form | V-ing form | 
| - - it ought not to happen - - - | - - it ought not to happening - - - | 
| Perfect | V-ing perfect | 
| - - it ought not to have happened - - - | - - it ought not to have been happening - - - | 
| Simple form | V-ing form | 
| - - ought to it happen? - - - | - - ought to it be happening? - - - | 
| Perfect | V-ing perfect | 
| - - ought to it have happened? - - - | - - ought to it have been happening? - - - | 
| Simple form | V-ing form | 
| - - ought it not to happen? - - - | - - ought it not to be happening? - - - | 
| Perfect | V-ing perfect | 
| - - ought it not to have happened? - - - | - - ought it not to have been happening? - - - |