can knock
Verbo regular: knock - knocked- knocked

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I can knock
you can knock
she can knock
we can knock
you can knock
they can knock 	I can be knocking
you can be knocking
she can be knocking
we can be knocking
you can be knocking
they can be knocking	I can have knocked
you can have knocked
she can have knocked
we can have knocked
you can have knocked
they can have knocked	I can have been knocking
you can have been knocking
she can have been knocking
we can have been knocking
you can have been knocking
they can have been knocking	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I cannot knock
you cannot knock
she cannot knock
we cannot knock
you cannot knock
they cannot knock 	I cannot be knocking
you cannot be knocking
she cannot be knocking
we cannot be knocking
you cannot be knocking
they cannot be knocking	I cannot have knocked
you cannot have knocked
she cannot have knocked
we cannot have knocked
you cannot have knocked
they cannot have knocked	I cannot have been knocking
you cannot have been knocking
she cannot have been knocking
we cannot have been knocking
you cannot have been knocking
they cannot have been knocking	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
can I knock?
can you knock?
can she knock?
can we knock?
can you knock?
can they knock? 	can I be knocking?
can you be knocking?
can she be knocking?
can we be knocking?
can you be knocking?
can they be knocking? 	can I have knocked?
can you have knocked?
can she have knocked?
can we have knocked?
can you have knocked?
can they have knocked? 	can I have been knocking?
can you have been knocking?
can she have been knocking?
can we have been knocking?
can you have been knocking?
can they have been knocking? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
can I not knock?
can you not knock?
can she not knock?
can we not knock?
can you not knock?
can they not knock? 	can I not be knocking?
can you not be knocking?
can she not be knocking?
can we not be knocking?
can you not be knocking?
can they not be knocking? 	can I not have knocked?
can you not have knocked?
can she not have knocked?
can we not have knocked?
can you not have knocked?
can they not have knocked? 	can I not have been knocking?
can you not have been knocking?
can she not have been knocking?
can we not have been knocking?
can you not have been knocking?
can they not have been knocking?