could quack
Verbo regular: quack - quacked- quacked

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could quack
you could quack
he could quack
we could quack
you could quack
they could quack 	I could be quacking
you could be quacking
he could be quacking
we could be quacking
you could be quacking
they could be quacking	I could have quacked
you could have quacked
he could have quacked
we could have quacked
you could have quacked
they could have quacked	I could have been quacking
you could have been quacking
he could have been quacking
we could have been quacking
you could have been quacking
they could have been quacking	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I couldn't quack
you couldn't quack
he couldn't quack
we couldn't quack
you couldn't quack
they couldn't quack 	I couldn't be quacking
you couldn't be quacking
he couldn't be quacking
we couldn't be quacking
you couldn't be quacking
they couldn't be quacking	I couldn't have quacked
you couldn't have quacked
he couldn't have quacked
we couldn't have quacked
you couldn't have quacked
they couldn't have quacked	I couldn't have been quacking
you couldn't have been quacking
he couldn't have been quacking
we couldn't have been quacking
you couldn't have been quacking
they couldn't have been quacking	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I quack?
could you quack?
could he quack?
could we quack?
could you quack?
could they quack? 	could I be quacking?
could you be quacking?
could he be quacking?
could we be quacking?
could you be quacking?
could they be quacking? 	could I have quacked?
could you have quacked?
could he have quacked?
could we have quacked?
could you have quacked?
could they have quacked? 	could I have been quacking?
could you have been quacking?
could he have been quacking?
could we have been quacking?
could you have been quacking?
could they have been quacking? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
couldn't I quack?
couldn't you quack?
couldn't he quack?
couldn't we quack?
couldn't you quack?
couldn't they quack? 	couldn't I be quacking?
couldn't you be quacking?
couldn't he be quacking?
couldn't we be quacking?
couldn't you be quacking?
couldn't they be quacking? 	couldn't I have quacked?
couldn't you have quacked?
couldn't he have quacked?
couldn't we have quacked?
couldn't you have quacked?
couldn't they have quacked? 	couldn't I have been quacking?
couldn't you have been quacking?
couldn't he have been quacking?
couldn't we have been quacking?
couldn't you have been quacking?
couldn't they have been quacking?