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