I must down you must down she must down we must down you must down they must down
V-ing form
I must be downing you must be downing she must be downing we must be downing you must be downing they must be downing
Perfect
I must have downed you must have downed she must have downed we must have downed you must have downed they must have downed
V-ing perfect
I must have been downing you must have been downing she must have been downing we must have been downing you must have been downing they must have been downing
Negation
Simple form
I must not down you must not down she must not down we must not down you must not down they must not down
V-ing form
I must not be downing you must not be downing she must not be downing we must not be downing you must not be downing they must not be downing
Perfect
I must not have downed you must not have downed she must not have downed we must not have downed you must not have downed they must not have downed
V-ing perfect
I must not have been downing you must not have been downing she must not have been downing we must not have been downing you must not have been downing they must not have been downing
Interrogative form
Simple form
must I down? must you down? must she down? must we down? must you down? must they down?
V-ing form
must I be downing? must you be downing? must she be downing? must we be downing? must you be downing? must they be downing?
Perfect
must I have downed? must you have downed? must she have downed? must we have downed? must you have downed? must they have downed?
V-ing perfect
must I have been downing? must you have been downing? must she have been downing? must we have been downing? must you have been downing? must they have been downing?
Interro-negative form
Simple form
must I not down? must you not down? must she not down? must we not down? must you not down? must they not down?
V-ing form
must I not be downing? must you not be downing? must she not be downing? must we not be downing? must you not be downing? must they not be downing?
Perfect
must I not have downed? must you not have downed? must she not have downed? must we not have downed? must you not have downed? must they not have downed?
V-ing perfect
must I not have been downing? must you not have been downing? must she not have been downing? must we not have been downing? must you not have been downing? must they not have been downing?