could sustain
Verbo regular: sustain - sustained- sustained

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I could sustain
you could sustain
he could sustain
we could sustain
you could sustain
they could sustain 	I could be sustaining
you could be sustaining
he could be sustaining
we could be sustaining
you could be sustaining
they could be sustaining	I could have sustained
you could have sustained
he could have sustained
we could have sustained
you could have sustained
they could have sustained	I could have been sustaining
you could have been sustaining
he could have been sustaining
we could have been sustaining
you could have been sustaining
they could have been sustaining	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I couldn't sustain
you couldn't sustain
he couldn't sustain
we couldn't sustain
you couldn't sustain
they couldn't sustain 	I couldn't be sustaining
you couldn't be sustaining
he couldn't be sustaining
we couldn't be sustaining
you couldn't be sustaining
they couldn't be sustaining	I couldn't have sustained
you couldn't have sustained
he couldn't have sustained
we couldn't have sustained
you couldn't have sustained
they couldn't have sustained	I couldn't have been sustaining
you couldn't have been sustaining
he couldn't have been sustaining
we couldn't have been sustaining
you couldn't have been sustaining
they couldn't have been sustaining	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
could I sustain?
could you sustain?
could he sustain?
could we sustain?
could you sustain?
could they sustain? 	could I be sustaining?
could you be sustaining?
could he be sustaining?
could we be sustaining?
could you be sustaining?
could they be sustaining? 	could I have sustained?
could you have sustained?
could he have sustained?
could we have sustained?
could you have sustained?
could they have sustained? 	could I have been sustaining?
could you have been sustaining?
could he have been sustaining?
could we have been sustaining?
could you have been sustaining?
could they have been sustaining? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
couldn't I sustain?
couldn't you sustain?
couldn't he sustain?
couldn't we sustain?
couldn't you sustain?
couldn't they sustain? 	couldn't I be sustaining?
couldn't you be sustaining?
couldn't he be sustaining?
couldn't we be sustaining?
couldn't you be sustaining?
couldn't they be sustaining? 	couldn't I have sustained?
couldn't you have sustained?
couldn't he have sustained?
couldn't we have sustained?
couldn't you have sustained?
couldn't they have sustained? 	couldn't I have been sustaining?
couldn't you have been sustaining?
couldn't he have been sustaining?
couldn't we have been sustaining?
couldn't you have been sustaining?
couldn't they have been sustaining?