English verb conjugation
COULD COMBINE

Regular verb: combine - combined - combined

Affirmation

Simple form	V-ing form
I could combine you could combine she could combine we could combine you could combine they could combine	I could be combining you could be combining she could be combining we could be combining you could be combining they could be combining
Perfect	V-ing perfect
I could have combined you could have combined she could have combined we could have combined you could have combined they could have combined	I could have been combining you could have been combining she could have been combining we could have been combining you could have been combining they could have been combining

Negation

Simple form	V-ing form
I couldn't combine you couldn't combine she couldn't combine we couldn't combine you couldn't combine they couldn't combine	I couldn't be combining you couldn't be combining she couldn't be combining we couldn't be combining you couldn't be combining they couldn't be combining
Perfect	V-ing perfect
I couldn't have combined you couldn't have combined she couldn't have combined we couldn't have combined you couldn't have combined they couldn't have combined	I couldn't have been combining you couldn't have been combining she couldn't have been combining we couldn't have been combining you couldn't have been combining they couldn't have been combining

Interrogative form

Simple form	V-ing form
could I combine? could you combine? could she combine? could we combine? could you combine? could they combine?	could I be combining? could you be combining? could she be combining? could we be combining? could you be combining? could they be combining?
Perfect	V-ing perfect
could I have combined? could you have combined? could she have combined? could we have combined? could you have combined? could they have combined?	could I have been combining? could you have been combining? could she have been combining? could we have been combining? could you have been combining? could they have been combining?

Interro-negative form

Simple form	V-ing form
couldn't I combine? couldn't you combine? couldn't she combine? couldn't we combine? couldn't you combine? couldn't they combine?	couldn't I be combining? couldn't you be combining? couldn't she be combining? couldn't we be combining? couldn't you be combining? couldn't they be combining?
Perfect	V-ing perfect
couldn't I have combined? couldn't you have combined? couldn't she have combined? couldn't we have combined? couldn't you have combined? couldn't they have combined?	couldn't I have been combining? couldn't you have been combining? couldn't she have been combining? couldn't we have been combining? couldn't you have been combining? couldn't they have been combining?