could modify
Verbo regular: modify - modified- modified

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
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	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	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I couldn't modify
you couldn't modify
he couldn't modify
we couldn't modify
you couldn't modify
they couldn't modify 	I couldn't be modifying
you couldn't be modifying
he couldn't be modifying
we couldn't be modifying
you couldn't be modifying
they couldn't be modifying	I couldn't have modified
you couldn't have modified
he couldn't have modified
we couldn't have modified
you couldn't have modified
they couldn't have modified	I couldn't have been modifying
you couldn't have been modifying
he couldn't have been modifying
we couldn't have been modifying
you couldn't have been modifying
they couldn't have been modifying	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
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? 	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? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
couldn't I modify?
couldn't you modify?
couldn't he modify?
couldn't we modify?
couldn't you modify?
couldn't they modify? 	couldn't I be modifying?
couldn't you be modifying?
couldn't he be modifying?
couldn't we be modifying?
couldn't you be modifying?
couldn't they be modifying? 	couldn't I have modified?
couldn't you have modified?
couldn't he have modified?
couldn't we have modified?
couldn't you have modified?
couldn't they have modified? 	couldn't I have been modifying?
couldn't you have been modifying?
couldn't he have been modifying?
couldn't we have been modifying?
couldn't you have been modifying?
couldn't they have been modifying?