I could pluck you could pluck he could pluck we could pluck you could pluck they could pluck
V-ing form
I could be plucking you could be plucking he could be plucking we could be plucking you could be plucking they could be plucking
Perfect
I could have plucked you could have plucked he could have plucked we could have plucked you could have plucked they could have plucked
V-ing perfect
I could have been plucking you could have been plucking he could have been plucking we could have been plucking you could have been plucking they could have been plucking
Negation
Simple form
I couldn't pluck you couldn't pluck he couldn't pluck we couldn't pluck you couldn't pluck they couldn't pluck
V-ing form
I couldn't be plucking you couldn't be plucking he couldn't be plucking we couldn't be plucking you couldn't be plucking they couldn't be plucking
Perfect
I couldn't have plucked you couldn't have plucked he couldn't have plucked we couldn't have plucked you couldn't have plucked they couldn't have plucked
V-ing perfect
I couldn't have been plucking you couldn't have been plucking he couldn't have been plucking we couldn't have been plucking you couldn't have been plucking they couldn't have been plucking
Interrogative form
Simple form
could I pluck? could you pluck? could he pluck? could we pluck? could you pluck? could they pluck?
V-ing form
could I be plucking? could you be plucking? could he be plucking? could we be plucking? could you be plucking? could they be plucking?
Perfect
could I have plucked? could you have plucked? could he have plucked? could we have plucked? could you have plucked? could they have plucked?
V-ing perfect
could I have been plucking? could you have been plucking? could he have been plucking? could we have been plucking? could you have been plucking? could they have been plucking?
Interro-negative form
Simple form
couldn't I pluck? couldn't you pluck? couldn't he pluck? couldn't we pluck? couldn't you pluck? couldn't they pluck?
V-ing form
couldn't I be plucking? couldn't you be plucking? couldn't he be plucking? couldn't we be plucking? couldn't you be plucking? couldn't they be plucking?
Perfect
couldn't I have plucked? couldn't you have plucked? couldn't he have plucked? couldn't we have plucked? couldn't you have plucked? couldn't they have plucked?
V-ing perfect
couldn't I have been plucking? couldn't you have been plucking? couldn't he have been plucking? couldn't we have been plucking? couldn't you have been plucking? couldn't they have been plucking?