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