could fasten
Verbo regular: fasten - fastened- fastened

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could fasten
you could fasten
he could fasten
we could fasten
you could fasten
they could fasten 	I could be fastening
you could be fastening
he could be fastening
we could be fastening
you could be fastening
they could be fastening	I could have fastened
you could have fastened
he could have fastened
we could have fastened
you could have fastened
they could have fastened	I could have been fastening
you could have been fastening
he could have been fastening
we could have been fastening
you could have been fastening
they could have been fastening	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could not fasten
you could not fasten
he could not fasten
we could not fasten
you could not fasten
they could not fasten 	I could not be fastening
you could not be fastening
he could not be fastening
we could not be fastening
you could not be fastening
they could not be fastening	I could not have fastened
you could not have fastened
he could not have fastened
we could not have fastened
you could not have fastened
they could not have fastened	I could not have been fastening
you could not have been fastening
he could not have been fastening
we could not have been fastening
you could not have been fastening
they could not have been fastening	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I fasten?
could you fasten?
could he fasten?
could we fasten?
could you fasten?
could they fasten? 	could I be fastening?
could you be fastening?
could he be fastening?
could we be fastening?
could you be fastening?
could they be fastening? 	could I have fastened?
could you have fastened?
could he have fastened?
could we have fastened?
could you have fastened?
could they have fastened? 	could I have been fastening?
could you have been fastening?
could he have been fastening?
could we have been fastening?
could you have been fastening?
could they have been fastening? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I not fasten?
could you not fasten?
could he not fasten?
could we not fasten?
could you not fasten?
could they not fasten? 	could I not be fastening?
could you not be fastening?
could he not be fastening?
could we not be fastening?
could you not be fastening?
could they not be fastening? 	could I not have fastened?
could you not have fastened?
could he not have fastened?
could we not have fastened?
could you not have fastened?
could they not have fastened? 	could I not have been fastening?
could you not have been fastening?
could he not have been fastening?
could we not have been fastening?
could you not have been fastening?
could they not have been fastening?