I must fold you must fold he must fold we must fold you must fold they must fold
V-ing form
I must be folding you must be folding he must be folding we must be folding you must be folding they must be folding
Perfect
I must have folded you must have folded he must have folded we must have folded you must have folded they must have folded
V-ing perfect
I must have been folding you must have been folding he must have been folding we must have been folding you must have been folding they must have been folding
Negation
Simple form
I must not fold you must not fold he must not fold we must not fold you must not fold they must not fold
V-ing form
I must not be folding you must not be folding he must not be folding we must not be folding you must not be folding they must not be folding
Perfect
I must not have folded you must not have folded he must not have folded we must not have folded you must not have folded they must not have folded
V-ing perfect
I must not have been folding you must not have been folding he must not have been folding we must not have been folding you must not have been folding they must not have been folding
Interrogative form
Simple form
must I fold? must you fold? must he fold? must we fold? must you fold? must they fold?
V-ing form
must I be folding? must you be folding? must he be folding? must we be folding? must you be folding? must they be folding?
Perfect
must I have folded? must you have folded? must he have folded? must we have folded? must you have folded? must they have folded?
V-ing perfect
must I have been folding? must you have been folding? must he have been folding? must we have been folding? must you have been folding? must they have been folding?
Interro-negative form
Simple form
must I not fold? must you not fold? must he not fold? must we not fold? must you not fold? must they not fold?
V-ing form
must I not be folding? must you not be folding? must he not be folding? must we not be folding? must you not be folding? must they not be folding?
Perfect
must I not have folded? must you not have folded? must he not have folded? must we not have folded? must you not have folded? must they not have folded?
V-ing perfect
must I not have been folding? must you not have been folding? must he not have been folding? must we not have been folding? must you not have been folding? must they not have been folding?