I could double you could double she could double we could double you could double they could double
V-ing form
I could be doubling you could be doubling she could be doubling we could be doubling you could be doubling they could be doubling
Perfect
I could have doubled you could have doubled she 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 she could have been doubling we could have been doubling you could have been doubling they could have been doubling
Negation
Simple form
I could not double you could not double she could not double we could not double you could not double they could not double
V-ing form
I could not be doubling you could not be doubling she could not be doubling we could not be doubling you could not be doubling they could not be doubling
Perfect
I could not have doubled you could not have doubled she could not have doubled we could not have doubled you could not have doubled they could not have doubled
V-ing perfect
I could not have been doubling you could not have been doubling she could not have been doubling we could not have been doubling you could not have been doubling they could not have been doubling
Interrogative form
Simple form
could I double? could you double? could she double? could we double? could you double? could they double?
V-ing form
could I be doubling? could you be doubling? could she be doubling? could we be doubling? could you be doubling? could they be doubling?
Perfect
could I have doubled? could you have doubled? could she 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 she have been doubling? could we have been doubling? could you have been doubling? could they have been doubling?
Interro-negative form
Simple form
could I not double? could you not double? could she not double? could we not double? could you not double? could they not double?
V-ing form
could I not be doubling? could you not be doubling? could she not be doubling? could we not be doubling? could you not be doubling? could they not be doubling?
Perfect
could I not have doubled? could you not have doubled? could she not have doubled? could we not have doubled? could you not have doubled? could they not have doubled?
V-ing perfect
could I not have been doubling? could you not have been doubling? could she not have been doubling? could we not have been doubling? could you not have been doubling? could they not have been doubling?