could alternate
Regular verb: alternate - alternated- alternated

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could alternate
you could alternate
she could alternate
we could alternate
you could alternate
they could alternate 	I could be alternating
you could be alternating
she could be alternating
we could be alternating
you could be alternating
they could be alternating	I could have alternated
you could have alternated
she could have alternated
we could have alternated
you could have alternated
they could have alternated	I could have been alternating
you could have been alternating
she could have been alternating
we could have been alternating
you could have been alternating
they could have been alternating	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't alternate
you couldn't alternate
she couldn't alternate
we couldn't alternate
you couldn't alternate
they couldn't alternate 	I couldn't be alternating
you couldn't be alternating
she couldn't be alternating
we couldn't be alternating
you couldn't be alternating
they couldn't be alternating	I couldn't have alternated
you couldn't have alternated
she couldn't have alternated
we couldn't have alternated
you couldn't have alternated
they couldn't have alternated	I couldn't have been alternating
you couldn't have been alternating
she couldn't have been alternating
we couldn't have been alternating
you couldn't have been alternating
they couldn't have been alternating	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I alternate?
could you alternate?
could she alternate?
could we alternate?
could you alternate?
could they alternate? 	could I be alternating?
could you be alternating?
could she be alternating?
could we be alternating?
could you be alternating?
could they be alternating? 	could I have alternated?
could you have alternated?
could she have alternated?
could we have alternated?
could you have alternated?
could they have alternated? 	could I have been alternating?
could you have been alternating?
could she have been alternating?
could we have been alternating?
could you have been alternating?
could they have been alternating? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I alternate?
couldn't you alternate?
couldn't she alternate?
couldn't we alternate?
couldn't you alternate?
couldn't they alternate? 	couldn't I be alternating?
couldn't you be alternating?
couldn't she be alternating?
couldn't we be alternating?
couldn't you be alternating?
couldn't they be alternating? 	couldn't I have alternated?
couldn't you have alternated?
couldn't she have alternated?
couldn't we have alternated?
couldn't you have alternated?
couldn't they have alternated? 	couldn't I have been alternating?
couldn't you have been alternating?
couldn't she have been alternating?
couldn't we have been alternating?
couldn't you have been alternating?
couldn't they have been alternating?