English verb conjugation
COULD COMBINE

Regular verb: combine - combined - combined

Affirmation

Simple form	V-ing form
I could combine you could combine he could combine we could combine you could combine they could combine	I could be combining you could be combining he 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 he 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 he 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 could not combine you could not combine he could not combine we could not combine you could not combine they could not combine	I could not be combining you could not be combining he could not be combining we could not be combining you could not be combining they could not be combining
Perfect	V-ing perfect
I could not have combined you could not have combined he could not have combined we could not have combined you could not have combined they could not have combined	I could not have been combining you could not have been combining he could not have been combining we could not have been combining you could not have been combining they could not have been combining

Interrogative form

Simple form	V-ing form
could I combine? could you combine? could he combine? could we combine? could you combine? could they combine?	could I be combining? could you be combining? could he 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 he 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 he 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
could I not combine? could you not combine? could he not combine? could we not combine? could you not combine? could they not combine?	could I not be combining? could you not be combining? could he not be combining? could we not be combining? could you not be combining? could they not be combining?
Perfect	V-ing perfect
could I not have combined? could you not have combined? could he not have combined? could we not have combined? could you not have combined? could they not have combined?	could I not have been combining? could you not have been combining? could he not have been combining? could we not have been combining? could you not have been combining? could they not have been combining?