could lengthen
Verbo regular: lengthen - lengthened- lengthened

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could lengthen
you could lengthen
he could lengthen
we could lengthen
you could lengthen
they could lengthen 	I could be lengthening
you could be lengthening
he could be lengthening
we could be lengthening
you could be lengthening
they could be lengthening	I could have lengthened
you could have lengthened
he could have lengthened
we could have lengthened
you could have lengthened
they could have lengthened	I could have been lengthening
you could have been lengthening
he could have been lengthening
we could have been lengthening
you could have been lengthening
they could have been lengthening	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I couldn't lengthen
you couldn't lengthen
he couldn't lengthen
we couldn't lengthen
you couldn't lengthen
they couldn't lengthen 	I couldn't be lengthening
you couldn't be lengthening
he couldn't be lengthening
we couldn't be lengthening
you couldn't be lengthening
they couldn't be lengthening	I couldn't have lengthened
you couldn't have lengthened
he couldn't have lengthened
we couldn't have lengthened
you couldn't have lengthened
they couldn't have lengthened	I couldn't have been lengthening
you couldn't have been lengthening
he couldn't have been lengthening
we couldn't have been lengthening
you couldn't have been lengthening
they couldn't have been lengthening	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I lengthen?
could you lengthen?
could he lengthen?
could we lengthen?
could you lengthen?
could they lengthen? 	could I be lengthening?
could you be lengthening?
could he be lengthening?
could we be lengthening?
could you be lengthening?
could they be lengthening? 	could I have lengthened?
could you have lengthened?
could he have lengthened?
could we have lengthened?
could you have lengthened?
could they have lengthened? 	could I have been lengthening?
could you have been lengthening?
could he have been lengthening?
could we have been lengthening?
could you have been lengthening?
could they have been lengthening? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
couldn't I lengthen?
couldn't you lengthen?
couldn't he lengthen?
couldn't we lengthen?
couldn't you lengthen?
couldn't they lengthen? 	couldn't I be lengthening?
couldn't you be lengthening?
couldn't he be lengthening?
couldn't we be lengthening?
couldn't you be lengthening?
couldn't they be lengthening? 	couldn't I have lengthened?
couldn't you have lengthened?
couldn't he have lengthened?
couldn't we have lengthened?
couldn't you have lengthened?
couldn't they have lengthened? 	couldn't I have been lengthening?
couldn't you have been lengthening?
couldn't he have been lengthening?
couldn't we have been lengthening?
couldn't you have been lengthening?
couldn't they have been lengthening?