I must sag you must sag he must sag we must sag you must sag they must sag
V-ing form
I must be sagging you must be sagging he must be sagging we must be sagging you must be sagging they must be sagging
Perfect
I must have sagged you must have sagged he must have sagged we must have sagged you must have sagged they must have sagged
V-ing perfect
I must have been sagging you must have been sagging he must have been sagging we must have been sagging you must have been sagging they must have been sagging
Negation
Simple form
I mustn't sag you mustn't sag he mustn't sag we mustn't sag you mustn't sag they mustn't sag
V-ing form
I mustn't be sagging you mustn't be sagging he mustn't be sagging we mustn't be sagging you mustn't be sagging they mustn't be sagging
Perfect
I mustn't have sagged you mustn't have sagged he mustn't have sagged we mustn't have sagged you mustn't have sagged they mustn't have sagged
V-ing perfect
I mustn't have been sagging you mustn't have been sagging he mustn't have been sagging we mustn't have been sagging you mustn't have been sagging they mustn't have been sagging
Interrogative form
Simple form
must I sag? must you sag? must he sag? must we sag? must you sag? must they sag?
V-ing form
must I be sagging? must you be sagging? must he be sagging? must we be sagging? must you be sagging? must they be sagging?
Perfect
must I have sagged? must you have sagged? must he have sagged? must we have sagged? must you have sagged? must they have sagged?
V-ing perfect
must I have been sagging? must you have been sagging? must he have been sagging? must we have been sagging? must you have been sagging? must they have been sagging?
Interro-negative form
Simple form
mustn't I sag? mustn't you sag? mustn't he sag? mustn't we sag? mustn't you sag? mustn't they sag?
V-ing form
mustn't I be sagging? mustn't you be sagging? mustn't he be sagging? mustn't we be sagging? mustn't you be sagging? mustn't they be sagging?
Perfect
mustn't I have sagged? mustn't you have sagged? mustn't he have sagged? mustn't we have sagged? mustn't you have sagged? mustn't they have sagged?
V-ing perfect
mustn't I have been sagging? mustn't you have been sagging? mustn't he have been sagging? mustn't we have been sagging? mustn't you have been sagging? mustn't they have been sagging?