I could suck you could suck he could suck we could suck you could suck they could suck
V-ing form
I could be sucking you could be sucking he could be sucking we could be sucking you could be sucking they could be sucking
Perfect
I could have sucked you could have sucked he could have sucked we could have sucked you could have sucked they could have sucked
V-ing perfect
I could have been sucking you could have been sucking he could have been sucking we could have been sucking you could have been sucking they could have been sucking
Negation
Simple form
I could not suck you could not suck he could not suck we could not suck you could not suck they could not suck
V-ing form
I could not be sucking you could not be sucking he could not be sucking we could not be sucking you could not be sucking they could not be sucking
Perfect
I could not have sucked you could not have sucked he could not have sucked we could not have sucked you could not have sucked they could not have sucked
V-ing perfect
I could not have been sucking you could not have been sucking he could not have been sucking we could not have been sucking you could not have been sucking they could not have been sucking
Interrogative form
Simple form
could I suck? could you suck? could he suck? could we suck? could you suck? could they suck?
V-ing form
could I be sucking? could you be sucking? could he be sucking? could we be sucking? could you be sucking? could they be sucking?
Perfect
could I have sucked? could you have sucked? could he have sucked? could we have sucked? could you have sucked? could they have sucked?
V-ing perfect
could I have been sucking? could you have been sucking? could he have been sucking? could we have been sucking? could you have been sucking? could they have been sucking?
Interro-negative form
Simple form
could I not suck? could you not suck? could he not suck? could we not suck? could you not suck? could they not suck?
V-ing form
could I not be sucking? could you not be sucking? could he not be sucking? could we not be sucking? could you not be sucking? could they not be sucking?
Perfect
could I not have sucked? could you not have sucked? could he not have sucked? could we not have sucked? could you not have sucked? could they not have sucked?
V-ing perfect
could I not have been sucking? could you not have been sucking? could he not have been sucking? could we not have been sucking? could you not have been sucking? could they not have been sucking?