
Verbo regular: happen - happened - happened
Forma simple | Forma con V-ing | 
| - - it may happen - - -  | - - it may be happening - - -  | 
Perfecto | Perfecto con V-ing | 
| - - it may have happened - - -  | - - it may have been happening - - -  | 
Forma simple | Forma con V-ing | 
| - - it may not happen - - -  | - - it may not be happening - - -  | 
Perfecto | Perfecto con V-ing | 
| - - it may not have happened - - -  | - - it may not have been happening - - -  | 
Forma simple | Forma con V-ing | 
| - - may it happen? - - -  | - - may it be happening? - - -  | 
Perfecto | Perfecto con V-ing | 
| - - may it have happened? - - -  | - - may it have been happening? - - -  | 
Forma simple | Forma con V-ing | 
| - - may it not happen? - - -  | - - may it not be happening? - - -  | 
Perfecto | Perfecto con V-ing | 
| - - may it not have happened? - - -  | - - may it not have been happening? - - -  |