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