could tremble
Verbo regular: tremble - trembled- trembled

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I could tremble
you could tremble
he could tremble
we could tremble
you could tremble
they could tremble 	I could be trembling
you could be trembling
he could be trembling
we could be trembling
you could be trembling
they could be trembling	I could have trembled
you could have trembled
he could have trembled
we could have trembled
you could have trembled
they could have trembled	I could have been trembling
you could have been trembling
he could have been trembling
we could have been trembling
you could have been trembling
they could have been trembling	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I could not tremble
you could not tremble
he could not tremble
we could not tremble
you could not tremble
they could not tremble 	I could not be trembling
you could not be trembling
he could not be trembling
we could not be trembling
you could not be trembling
they could not be trembling	I could not have trembled
you could not have trembled
he could not have trembled
we could not have trembled
you could not have trembled
they could not have trembled	I could not have been trembling
you could not have been trembling
he could not have been trembling
we could not have been trembling
you could not have been trembling
they could not have been trembling	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
could I tremble?
could you tremble?
could he tremble?
could we tremble?
could you tremble?
could they tremble? 	could I be trembling?
could you be trembling?
could he be trembling?
could we be trembling?
could you be trembling?
could they be trembling? 	could I have trembled?
could you have trembled?
could he have trembled?
could we have trembled?
could you have trembled?
could they have trembled? 	could I have been trembling?
could you have been trembling?
could he have been trembling?
could we have been trembling?
could you have been trembling?
could they have been trembling? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
could I not tremble?
could you not tremble?
could he not tremble?
could we not tremble?
could you not tremble?
could they not tremble? 	could I not be trembling?
could you not be trembling?
could he not be trembling?
could we not be trembling?
could you not be trembling?
could they not be trembling? 	could I not have trembled?
could you not have trembled?
could he not have trembled?
could we not have trembled?
could you not have trembled?
could they not have trembled? 	could I not have been trembling?
could you not have been trembling?
could he not have been trembling?
could we not have been trembling?
could you not have been trembling?
could they not have been trembling?