English verb conjugation
COULD MODIFY

Regular verb: modify - modified - modified

Affirmation

Simple form	V-ing form
I could modify you could modify he could modify we could modify you could modify they could modify	I could be modifying you could be modifying he could be modifying we could be modifying you could be modifying they could be modifying
Perfect	V-ing perfect
I could have modified you could have modified he could have modified we could have modified you could have modified they could have modified	I could have been modifying you could have been modifying he could have been modifying we could have been modifying you could have been modifying they could have been modifying

Negation

Simple form	V-ing form
I could not modify you could not modify he could not modify we could not modify you could not modify they could not modify	I could not be modifying you could not be modifying he could not be modifying we could not be modifying you could not be modifying they could not be modifying
Perfect	V-ing perfect
I could not have modified you could not have modified he could not have modified we could not have modified you could not have modified they could not have modified	I could not have been modifying you could not have been modifying he could not have been modifying we could not have been modifying you could not have been modifying they could not have been modifying

Interrogative form

Simple form	V-ing form
could I modify? could you modify? could he modify? could we modify? could you modify? could they modify?	could I be modifying? could you be modifying? could he be modifying? could we be modifying? could you be modifying? could they be modifying?
Perfect	V-ing perfect
could I have modified? could you have modified? could he have modified? could we have modified? could you have modified? could they have modified?	could I have been modifying? could you have been modifying? could he have been modifying? could we have been modifying? could you have been modifying? could they have been modifying?

Interro-negative form

Simple form	V-ing form
could I not modify? could you not modify? could he not modify? could we not modify? could you not modify? could they not modify?	could I not be modifying? could you not be modifying? could he not be modifying? could we not be modifying? could you not be modifying? could they not be modifying?
Perfect	V-ing perfect
could I not have modified? could you not have modified? could he not have modified? could we not have modified? could you not have modified? could they not have modified?	could I not have been modifying? could you not have been modifying? could he not have been modifying? could we not have been modifying? could you not have been modifying? could they not have been modifying?