could echo
Regular verb: echo - echoed- echoed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could echo
you could echo
he could echo
we could echo
you could echo
they could echo 	I could be echoing
you could be echoing
he could be echoing
we could be echoing
you could be echoing
they could be echoing	I could have echoed
you could have echoed
he could have echoed
we could have echoed
you could have echoed
they could have echoed	I could have been echoing
you could have been echoing
he could have been echoing
we could have been echoing
you could have been echoing
they could have been echoing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not echo
you could not echo
he could not echo
we could not echo
you could not echo
they could not echo 	I could not be echoing
you could not be echoing
he could not be echoing
we could not be echoing
you could not be echoing
they could not be echoing	I could not have echoed
you could not have echoed
he could not have echoed
we could not have echoed
you could not have echoed
they could not have echoed	I could not have been echoing
you could not have been echoing
he could not have been echoing
we could not have been echoing
you could not have been echoing
they could not have been echoing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I echo?
could you echo?
could he echo?
could we echo?
could you echo?
could they echo? 	could I be echoing?
could you be echoing?
could he be echoing?
could we be echoing?
could you be echoing?
could they be echoing? 	could I have echoed?
could you have echoed?
could he have echoed?
could we have echoed?
could you have echoed?
could they have echoed? 	could I have been echoing?
could you have been echoing?
could he have been echoing?
could we have been echoing?
could you have been echoing?
could they have been echoing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not echo?
could you not echo?
could he not echo?
could we not echo?
could you not echo?
could they not echo? 	could I not be echoing?
could you not be echoing?
could he not be echoing?
could we not be echoing?
could you not be echoing?
could they not be echoing? 	could I not have echoed?
could you not have echoed?
could he not have echoed?
could we not have echoed?
could you not have echoed?
could they not have echoed? 	could I not have been echoing?
could you not have been echoing?
could he not have been echoing?
could we not have been echoing?
could you not have been echoing?
could they not have been echoing?