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