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 could not quack
you could not quack
he could not quack
we could not quack
you could not quack
they could not quack 	I could not be quacking
you could not be quacking
he could not be quacking
we could not be quacking
you could not be quacking
they could not be quacking	I could not have quacked
you could not have quacked
he could not have quacked
we could not have quacked
you could not have quacked
they could not have quacked	I could not have been quacking
you could not have been quacking
he could not have been quacking
we could not have been quacking
you could not have been quacking
they could not 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 	
could I not quack?
could you not quack?
could he not quack?
could we not quack?
could you not quack?
could they not quack? 	could I not be quacking?
could you not be quacking?
could he not be quacking?
could we not be quacking?
could you not be quacking?
could they not be quacking? 	could I not have quacked?
could you not have quacked?
could he not have quacked?
could we not have quacked?
could you not have quacked?
could they not have quacked? 	could I not have been quacking?
could you not have been quacking?
could he not have been quacking?
could we not have been quacking?
could you not have been quacking?
could they not have been quacking?