Regular verb: happen - happened - happened
Simple form | V-ing form |
- - it'd happen - - - | - - it'd be happening - - - |
Perfect | V-ing perfect |
- - it should've happened - - - | - - it should've been happening - - - |
Simple form | V-ing form |
- - it shouldn't happen - - - | - - it shouldn't be happening - - - |
Perfect | V-ing perfect |
- - it shouldn't have happened - - - | - - it shouldn't have been happening - - - |
Simple form | V-ing form |
- - should it happen? - - - | - - should it be happening? - - - |
Perfect | V-ing perfect |
- - should it have happened? - - - | - - should it have been happening? - - - |
Simple form | V-ing form |
- - shouldn't it happen? - - - | - - shouldn't it be happening? - - - |
Perfect | V-ing perfect |
- - shouldn't it have happened? - - - | - - shouldn't it have been happening? - - - |