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