could use
Regular verb: use - used- used

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could use
you could use
she could use
we could use
you could use
they could use 	I could be using
you could be using
she could be using
we could be using
you could be using
they could be using	I could have used
you could have used
she could have used
we could have used
you could have used
they could have used	I could have been using
you could have been using
she could have been using
we could have been using
you could have been using
they could have been using	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not use
you could not use
she could not use
we could not use
you could not use
they could not use 	I could not be using
you could not be using
she could not be using
we could not be using
you could not be using
they could not be using	I could not have used
you could not have used
she could not have used
we could not have used
you could not have used
they could not have used	I could not have been using
you could not have been using
she could not have been using
we could not have been using
you could not have been using
they could not have been using	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I use?
could you use?
could she use?
could we use?
could you use?
could they use? 	could I be using?
could you be using?
could she be using?
could we be using?
could you be using?
could they be using? 	could I have used?
could you have used?
could she have used?
could we have used?
could you have used?
could they have used? 	could I have been using?
could you have been using?
could she have been using?
could we have been using?
could you have been using?
could they have been using? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not use?
could you not use?
could she not use?
could we not use?
could you not use?
could they not use? 	could I not be using?
could you not be using?
could she not be using?
could we not be using?
could you not be using?
could they not be using? 	could I not have used?
could you not have used?
could she not have used?
could we not have used?
could you not have used?
could they not have used? 	could I not have been using?
could you not have been using?
could she not have been using?
could we not have been using?
could you not have been using?
could they not have been using?