I must crouch you must crouch he must crouch we must crouch you must crouch they must crouch
V-ing form
I must be crouching you must be crouching he must be crouching we must be crouching you must be crouching they must be crouching
Perfect
I must have crouched you must have crouched he 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 he must have been crouching we must have been crouching you must have been crouching they must have been crouching
Negation
Simple form
I must not crouch you must not crouch he must not crouch we must not crouch you must not crouch they must not crouch
V-ing form
I must not be crouching you must not be crouching he must not be crouching we must not be crouching you must not be crouching they must not be crouching
Perfect
I must not have crouched you must not have crouched he must not have crouched we must not have crouched you must not have crouched they must not have crouched
V-ing perfect
I must not have been crouching you must not have been crouching he must not have been crouching we must not have been crouching you must not have been crouching they must not have been crouching
Interrogative form
Simple form
must I crouch? must you crouch? must he crouch? must we crouch? must you crouch? must they crouch?
V-ing form
must I be crouching? must you be crouching? must he be crouching? must we be crouching? must you be crouching? must they be crouching?
Perfect
must I have crouched? must you have crouched? must he 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 he have been crouching? must we have been crouching? must you have been crouching? must they have been crouching?
Interro-negative form
Simple form
must I not crouch? must you not crouch? must he not crouch? must we not crouch? must you not crouch? must they not crouch?
V-ing form
must I not be crouching? must you not be crouching? must he not be crouching? must we not be crouching? must you not be crouching? must they not be crouching?
Perfect
must I not have crouched? must you not have crouched? must he not have crouched? must we not have crouched? must you not have crouched? must they not have crouched?
V-ing perfect
must I not have been crouching? must you not have been crouching? must he not have been crouching? must we not have been crouching? must you not have been crouching? must they not have been crouching?