I must flash you must flash he must flash we must flash you must flash they must flash
V-ing form
I must be flashing you must be flashing he must be flashing we must be flashing you must be flashing they must be flashing
Perfect
I must have flashed you must have flashed he must have flashed we must have flashed you must have flashed they must have flashed
V-ing perfect
I must have been flashing you must have been flashing he must have been flashing we must have been flashing you must have been flashing they must have been flashing
Negation
Simple form
I mustn't flash you mustn't flash he mustn't flash we mustn't flash you mustn't flash they mustn't flash
V-ing form
I mustn't be flashing you mustn't be flashing he mustn't be flashing we mustn't be flashing you mustn't be flashing they mustn't be flashing
Perfect
I mustn't have flashed you mustn't have flashed he mustn't have flashed we mustn't have flashed you mustn't have flashed they mustn't have flashed
V-ing perfect
I mustn't have been flashing you mustn't have been flashing he mustn't have been flashing we mustn't have been flashing you mustn't have been flashing they mustn't have been flashing
Interrogative form
Simple form
must I flash? must you flash? must he flash? must we flash? must you flash? must they flash?
V-ing form
must I be flashing? must you be flashing? must he be flashing? must we be flashing? must you be flashing? must they be flashing?
Perfect
must I have flashed? must you have flashed? must he have flashed? must we have flashed? must you have flashed? must they have flashed?
V-ing perfect
must I have been flashing? must you have been flashing? must he have been flashing? must we have been flashing? must you have been flashing? must they have been flashing?
Interro-negative form
Simple form
mustn't I flash? mustn't you flash? mustn't he flash? mustn't we flash? mustn't you flash? mustn't they flash?
V-ing form
mustn't I be flashing? mustn't you be flashing? mustn't he be flashing? mustn't we be flashing? mustn't you be flashing? mustn't they be flashing?
Perfect
mustn't I have flashed? mustn't you have flashed? mustn't he have flashed? mustn't we have flashed? mustn't you have flashed? mustn't they have flashed?
V-ing perfect
mustn't I have been flashing? mustn't you have been flashing? mustn't he have been flashing? mustn't we have been flashing? mustn't you have been flashing? mustn't they have been flashing?