I could milk you could milk he could milk we could milk you could milk they could milk
V-ing form
I could be milking you could be milking he could be milking we could be milking you could be milking they could be milking
Perfect
I could have milked you could have milked he could have milked we could have milked you could have milked they could have milked
V-ing perfect
I could have been milking you could have been milking he could have been milking we could have been milking you could have been milking they could have been milking
Negation
Simple form
I could not milk you could not milk he could not milk we could not milk you could not milk they could not milk
V-ing form
I could not be milking you could not be milking he could not be milking we could not be milking you could not be milking they could not be milking
Perfect
I could not have milked you could not have milked he could not have milked we could not have milked you could not have milked they could not have milked
V-ing perfect
I could not have been milking you could not have been milking he could not have been milking we could not have been milking you could not have been milking they could not have been milking
Interrogative form
Simple form
could I milk? could you milk? could he milk? could we milk? could you milk? could they milk?
V-ing form
could I be milking? could you be milking? could he be milking? could we be milking? could you be milking? could they be milking?
Perfect
could I have milked? could you have milked? could he have milked? could we have milked? could you have milked? could they have milked?
V-ing perfect
could I have been milking? could you have been milking? could he have been milking? could we have been milking? could you have been milking? could they have been milking?
Interro-negative form
Simple form
could I not milk? could you not milk? could he not milk? could we not milk? could you not milk? could they not milk?
V-ing form
could I not be milking? could you not be milking? could he not be milking? could we not be milking? could you not be milking? could they not be milking?
Perfect
could I not have milked? could you not have milked? could he not have milked? could we not have milked? could you not have milked? could they not have milked?
V-ing perfect
could I not have been milking? could you not have been milking? could he not have been milking? could we not have been milking? could you not have been milking? could they not have been milking?