I must duck you must duck she must duck we must duck you must duck they must duck
V-ing form
I must be ducking you must be ducking she must be ducking we must be ducking you must be ducking they must be ducking
Perfect
I must have ducked you must have ducked she must have ducked we must have ducked you must have ducked they must have ducked
V-ing perfect
I must have been ducking you must have been ducking she must have been ducking we must have been ducking you must have been ducking they must have been ducking
Negation
Simple form
I must not duck you must not duck she must not duck we must not duck you must not duck they must not duck
V-ing form
I must not be ducking you must not be ducking she must not be ducking we must not be ducking you must not be ducking they must not be ducking
Perfect
I must not have ducked you must not have ducked she must not have ducked we must not have ducked you must not have ducked they must not have ducked
V-ing perfect
I must not have been ducking you must not have been ducking she must not have been ducking we must not have been ducking you must not have been ducking they must not have been ducking
Interrogative form
Simple form
must I duck? must you duck? must she duck? must we duck? must you duck? must they duck?
V-ing form
must I be ducking? must you be ducking? must she be ducking? must we be ducking? must you be ducking? must they be ducking?
Perfect
must I have ducked? must you have ducked? must she have ducked? must we have ducked? must you have ducked? must they have ducked?
V-ing perfect
must I have been ducking? must you have been ducking? must she have been ducking? must we have been ducking? must you have been ducking? must they have been ducking?
Interro-negative form
Simple form
must I not duck? must you not duck? must she not duck? must we not duck? must you not duck? must they not duck?
V-ing form
must I not be ducking? must you not be ducking? must she not be ducking? must we not be ducking? must you not be ducking? must they not be ducking?
Perfect
must I not have ducked? must you not have ducked? must she not have ducked? must we not have ducked? must you not have ducked? must they not have ducked?
V-ing perfect
must I not have been ducking? must you not have been ducking? must she not have been ducking? must we not have been ducking? must you not have been ducking? must they not have been ducking?