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 must not suck you must not suck he must not suck we must not suck you must not suck they must not suck
V-ing form
I must not be sucking you must not be sucking he must not be sucking we must not be sucking you must not be sucking they must not be sucking
Perfect
I must not have sucked you must not have sucked he must not have sucked we must not have sucked you must not have sucked they must not have sucked
V-ing perfect
I must not have been sucking you must not have been sucking he must not have been sucking we must not have been sucking you must not have been sucking they must not 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
must I not suck? must you not suck? must he not suck? must we not suck? must you not suck? must they not suck?
V-ing form
must I not be sucking? must you not be sucking? must he not be sucking? must we not be sucking? must you not be sucking? must they not be sucking?
Perfect
must I not have sucked? must you not have sucked? must he not have sucked? must we not have sucked? must you not have sucked? must they not have sucked?
V-ing perfect
must I not have been sucking? must you not have been sucking? must he not have been sucking? must we not have been sucking? must you not have been sucking? must they not have been sucking?