could substitute
Verbo regular: substitute - substituted- substituted

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I could substitute
you could substitute
he could substitute
we could substitute
you could substitute
they could substitute 	I could be substituting
you could be substituting
he could be substituting
we could be substituting
you could be substituting
they could be substituting	I could have substituted
you could have substituted
he could have substituted
we could have substituted
you could have substituted
they could have substituted	I could have been substituting
you could have been substituting
he could have been substituting
we could have been substituting
you could have been substituting
they could have been substituting	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I couldn't substitute
you couldn't substitute
he couldn't substitute
we couldn't substitute
you couldn't substitute
they couldn't substitute 	I couldn't be substituting
you couldn't be substituting
he couldn't be substituting
we couldn't be substituting
you couldn't be substituting
they couldn't be substituting	I couldn't have substituted
you couldn't have substituted
he couldn't have substituted
we couldn't have substituted
you couldn't have substituted
they couldn't have substituted	I couldn't have been substituting
you couldn't have been substituting
he couldn't have been substituting
we couldn't have been substituting
you couldn't have been substituting
they couldn't have been substituting	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
could I substitute?
could you substitute?
could he substitute?
could we substitute?
could you substitute?
could they substitute? 	could I be substituting?
could you be substituting?
could he be substituting?
could we be substituting?
could you be substituting?
could they be substituting? 	could I have substituted?
could you have substituted?
could he have substituted?
could we have substituted?
could you have substituted?
could they have substituted? 	could I have been substituting?
could you have been substituting?
could he have been substituting?
could we have been substituting?
could you have been substituting?
could they have been substituting? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
couldn't I substitute?
couldn't you substitute?
couldn't he substitute?
couldn't we substitute?
couldn't you substitute?
couldn't they substitute? 	couldn't I be substituting?
couldn't you be substituting?
couldn't he be substituting?
couldn't we be substituting?
couldn't you be substituting?
couldn't they be substituting? 	couldn't I have substituted?
couldn't you have substituted?
couldn't he have substituted?
couldn't we have substituted?
couldn't you have substituted?
couldn't they have substituted? 	couldn't I have been substituting?
couldn't you have been substituting?
couldn't he have been substituting?
couldn't we have been substituting?
couldn't you have been substituting?
couldn't they have been substituting?