
Irregular verb: be - was/were - been
Simple form | V-ing form | 
| I must be you must be he must be we must be you must be they must be  | I must be being you must be being he must be being we must be being you must be being they must be being  | 
Perfect | V-ing perfect | 
| I must have been you must have been he must have been we must have been you must have been they must have been  | I must have been being you must have been being he must have been being we must have been being you must have been being they must have been being  | 
Simple form | V-ing form | 
| I mustn't be you mustn't be he mustn't be we mustn't be you mustn't be they mustn't be  | I mustn't be being you mustn't be being he mustn't be being we mustn't be being you mustn't be being they mustn't be being  | 
Perfect | V-ing perfect | 
| I mustn't have been you mustn't have been he mustn't have been we mustn't have been you mustn't have been they mustn't have been  | I mustn't have been being you mustn't have been being he mustn't have been being we mustn't have been being you mustn't have been being they mustn't have been being  | 
Simple form | V-ing form | 
| must I be? must you be? must he be? must we be? must you be? must they be?  | must I be being? must you be being? must he be being? must we be being? must you be being? must they be being?  | 
Perfect | V-ing perfect | 
| must I have been? must you have been? must he have been? must we have been? must you have been? must they have been?  | must I have been being? must you have been being? must he have been being? must we have been being? must you have been being? must they have been being?  | 
Simple form | V-ing form | 
| mustn't I be? mustn't you be? mustn't he be? mustn't we be? mustn't you be? mustn't they be?  | mustn't I be being? mustn't you be being? mustn't he be being? mustn't we be being? mustn't you be being? mustn't they be being?  | 
Perfect | V-ing perfect | 
| mustn't I have been? mustn't you have been? mustn't he have been? mustn't we have been? mustn't you have been? mustn't they have been?  | mustn't I have been being? mustn't you have been being? mustn't he have been being? mustn't we have been being? mustn't you have been being? mustn't they have been being?  |