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 couldn't milk you couldn't milk he couldn't milk we couldn't milk you couldn't milk they couldn't milk
V-ing form
I couldn't be milking you couldn't be milking he couldn't be milking we couldn't be milking you couldn't be milking they couldn't be milking
Perfect
I couldn't have milked you couldn't have milked he couldn't have milked we couldn't have milked you couldn't have milked they couldn't have milked
V-ing perfect
I couldn't have been milking you couldn't have been milking he couldn't have been milking we couldn't have been milking you couldn't have been milking they couldn't 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
couldn't I milk? couldn't you milk? couldn't he milk? couldn't we milk? couldn't you milk? couldn't they milk?
V-ing form
couldn't I be milking? couldn't you be milking? couldn't he be milking? couldn't we be milking? couldn't you be milking? couldn't they be milking?
Perfect
couldn't I have milked? couldn't you have milked? couldn't he have milked? couldn't we have milked? couldn't you have milked? couldn't they have milked?
V-ing perfect
couldn't I have been milking? couldn't you have been milking? couldn't he have been milking? couldn't we have been milking? couldn't you have been milking? couldn't they have been milking?