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