could tube
Verbo regular: tube - tubed- tubed

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I could tube
you could tube
he could tube
we could tube
you could tube
they could tube 	I could be tubing
you could be tubing
he could be tubing
we could be tubing
you could be tubing
they could be tubing	I could have tubed
you could have tubed
he could have tubed
we could have tubed
you could have tubed
they could have tubed	I could have been tubing
you could have been tubing
he could have been tubing
we could have been tubing
you could have been tubing
they could have been tubing	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I could not tube
you could not tube
he could not tube
we could not tube
you could not tube
they could not tube 	I could not be tubing
you could not be tubing
he could not be tubing
we could not be tubing
you could not be tubing
they could not be tubing	I could not have tubed
you could not have tubed
he could not have tubed
we could not have tubed
you could not have tubed
they could not have tubed	I could not have been tubing
you could not have been tubing
he could not have been tubing
we could not have been tubing
you could not have been tubing
they could not have been tubing	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
could I tube?
could you tube?
could he tube?
could we tube?
could you tube?
could they tube? 	could I be tubing?
could you be tubing?
could he be tubing?
could we be tubing?
could you be tubing?
could they be tubing? 	could I have tubed?
could you have tubed?
could he have tubed?
could we have tubed?
could you have tubed?
could they have tubed? 	could I have been tubing?
could you have been tubing?
could he have been tubing?
could we have been tubing?
could you have been tubing?
could they have been tubing? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
could I not tube?
could you not tube?
could he not tube?
could we not tube?
could you not tube?
could they not tube? 	could I not be tubing?
could you not be tubing?
could he not be tubing?
could we not be tubing?
could you not be tubing?
could they not be tubing? 	could I not have tubed?
could you not have tubed?
could he not have tubed?
could we not have tubed?
could you not have tubed?
could they not have tubed? 	could I not have been tubing?
could you not have been tubing?
could he not have been tubing?
could we not have been tubing?
could you not have been tubing?
could they not have been tubing?