English verb conjugation
CAN MODIFY

Regular verb: modify - modified - modified

Affirmation

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

Negation

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

Interrogative form

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

Interro-negative form

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