I must crouch you must crouch she must crouch we must crouch you must crouch they must crouch
V-ing form
I must be crouching you must be crouching she must be crouching we must be crouching you must be crouching they must be crouching
Perfect
I must have crouched you must have crouched she must have crouched we must have crouched you must have crouched they must have crouched
V-ing perfect
I must have been crouching you must have been crouching she must have been crouching we must have been crouching you must have been crouching they must have been crouching
Negation
Simple form
I mustn't crouch you mustn't crouch she mustn't crouch we mustn't crouch you mustn't crouch they mustn't crouch
V-ing form
I mustn't be crouching you mustn't be crouching she mustn't be crouching we mustn't be crouching you mustn't be crouching they mustn't be crouching
Perfect
I mustn't have crouched you mustn't have crouched she mustn't have crouched we mustn't have crouched you mustn't have crouched they mustn't have crouched
V-ing perfect
I mustn't have been crouching you mustn't have been crouching she mustn't have been crouching we mustn't have been crouching you mustn't have been crouching they mustn't have been crouching
Interrogative form
Simple form
must I crouch? must you crouch? must she crouch? must we crouch? must you crouch? must they crouch?
V-ing form
must I be crouching? must you be crouching? must she be crouching? must we be crouching? must you be crouching? must they be crouching?
Perfect
must I have crouched? must you have crouched? must she have crouched? must we have crouched? must you have crouched? must they have crouched?
V-ing perfect
must I have been crouching? must you have been crouching? must she have been crouching? must we have been crouching? must you have been crouching? must they have been crouching?
Interro-negative form
Simple form
mustn't I crouch? mustn't you crouch? mustn't she crouch? mustn't we crouch? mustn't you crouch? mustn't they crouch?
V-ing form
mustn't I be crouching? mustn't you be crouching? mustn't she be crouching? mustn't we be crouching? mustn't you be crouching? mustn't they be crouching?
Perfect
mustn't I have crouched? mustn't you have crouched? mustn't she have crouched? mustn't we have crouched? mustn't you have crouched? mustn't they have crouched?
V-ing perfect
mustn't I have been crouching? mustn't you have been crouching? mustn't she have been crouching? mustn't we have been crouching? mustn't you have been crouching? mustn't they have been crouching?