could ascertain
Verbo regular: ascertain - ascertained- ascertained

Afirmação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could ascertain
you could ascertain
he could ascertain
we could ascertain
you could ascertain
they could ascertain 	I could be ascertaining
you could be ascertaining
he could be ascertaining
we could be ascertaining
you could be ascertaining
they could be ascertaining	I could have ascertained
you could have ascertained
he could have ascertained
we could have ascertained
you could have ascertained
they could have ascertained	I could have been ascertaining
you could have been ascertaining
he could have been ascertaining
we could have been ascertaining
you could have been ascertaining
they could have been ascertaining	

Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
I could not ascertain
you could not ascertain
he could not ascertain
we could not ascertain
you could not ascertain
they could not ascertain 	I could not be ascertaining
you could not be ascertaining
he could not be ascertaining
we could not be ascertaining
you could not be ascertaining
they could not be ascertaining	I could not have ascertained
you could not have ascertained
he could not have ascertained
we could not have ascertained
you could not have ascertained
they could not have ascertained	I could not have been ascertaining
you could not have been ascertaining
he could not have been ascertaining
we could not have been ascertaining
you could not have been ascertaining
they could not have been ascertaining	

Forma interrogativa 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I ascertain?
could you ascertain?
could he ascertain?
could we ascertain?
could you ascertain?
could they ascertain? 	could I be ascertaining?
could you be ascertaining?
could he be ascertaining?
could we be ascertaining?
could you be ascertaining?
could they be ascertaining? 	could I have ascertained?
could you have ascertained?
could he have ascertained?
could we have ascertained?
could you have ascertained?
could they have ascertained? 	could I have been ascertaining?
could you have been ascertaining?
could he have been ascertaining?
could we have been ascertaining?
could you have been ascertaining?
could they have been ascertaining? 	

Forma interro-Negação 	
Forma simple 	Forma com V-ing 	Perfeito 	Perfeito com V-ing 	
could I not ascertain?
could you not ascertain?
could he not ascertain?
could we not ascertain?
could you not ascertain?
could they not ascertain? 	could I not be ascertaining?
could you not be ascertaining?
could he not be ascertaining?
could we not be ascertaining?
could you not be ascertaining?
could they not be ascertaining? 	could I not have ascertained?
could you not have ascertained?
could he not have ascertained?
could we not have ascertained?
could you not have ascertained?
could they not have ascertained? 	could I not have been ascertaining?
could you not have been ascertaining?
could he not have been ascertaining?
could we not have been ascertaining?
could you not have been ascertaining?
could they not have been ascertaining?