could filter
Verbo regular: filter - filtered- filtered

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could filter
you could filter
he could filter
we could filter
you could filter
they could filter 	I could be filtering
you could be filtering
he could be filtering
we could be filtering
you could be filtering
they could be filtering	I could have filtered
you could have filtered
he could have filtered
we could have filtered
you could have filtered
they could have filtered	I could have been filtering
you could have been filtering
he could have been filtering
we could have been filtering
you could have been filtering
they could have been filtering	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I couldn't filter
you couldn't filter
he couldn't filter
we couldn't filter
you couldn't filter
they couldn't filter 	I couldn't be filtering
you couldn't be filtering
he couldn't be filtering
we couldn't be filtering
you couldn't be filtering
they couldn't be filtering	I couldn't have filtered
you couldn't have filtered
he couldn't have filtered
we couldn't have filtered
you couldn't have filtered
they couldn't have filtered	I couldn't have been filtering
you couldn't have been filtering
he couldn't have been filtering
we couldn't have been filtering
you couldn't have been filtering
they couldn't have been filtering	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I filter?
could you filter?
could he filter?
could we filter?
could you filter?
could they filter? 	could I be filtering?
could you be filtering?
could he be filtering?
could we be filtering?
could you be filtering?
could they be filtering? 	could I have filtered?
could you have filtered?
could he have filtered?
could we have filtered?
could you have filtered?
could they have filtered? 	could I have been filtering?
could you have been filtering?
could he have been filtering?
could we have been filtering?
could you have been filtering?
could they have been filtering? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
couldn't I filter?
couldn't you filter?
couldn't he filter?
couldn't we filter?
couldn't you filter?
couldn't they filter? 	couldn't I be filtering?
couldn't you be filtering?
couldn't he be filtering?
couldn't we be filtering?
couldn't you be filtering?
couldn't they be filtering? 	couldn't I have filtered?
couldn't you have filtered?
couldn't he have filtered?
couldn't we have filtered?
couldn't you have filtered?
couldn't they have filtered? 	couldn't I have been filtering?
couldn't you have been filtering?
couldn't he have been filtering?
couldn't we have been filtering?
couldn't you have been filtering?
couldn't they have been filtering?