could abstain
Regular verb: abstain - abstained- abstained

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could abstain
you could abstain
she could abstain
we could abstain
you could abstain
they could abstain 	I could be abstaining
you could be abstaining
she could be abstaining
we could be abstaining
you could be abstaining
they could be abstaining	I could have abstained
you could have abstained
she could have abstained
we could have abstained
you could have abstained
they could have abstained	I could have been abstaining
you could have been abstaining
she could have been abstaining
we could have been abstaining
you could have been abstaining
they could have been abstaining	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't abstain
you couldn't abstain
she couldn't abstain
we couldn't abstain
you couldn't abstain
they couldn't abstain 	I couldn't be abstaining
you couldn't be abstaining
she couldn't be abstaining
we couldn't be abstaining
you couldn't be abstaining
they couldn't be abstaining	I couldn't have abstained
you couldn't have abstained
she couldn't have abstained
we couldn't have abstained
you couldn't have abstained
they couldn't have abstained	I couldn't have been abstaining
you couldn't have been abstaining
she couldn't have been abstaining
we couldn't have been abstaining
you couldn't have been abstaining
they couldn't have been abstaining	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I abstain?
could you abstain?
could she abstain?
could we abstain?
could you abstain?
could they abstain? 	could I be abstaining?
could you be abstaining?
could she be abstaining?
could we be abstaining?
could you be abstaining?
could they be abstaining? 	could I have abstained?
could you have abstained?
could she have abstained?
could we have abstained?
could you have abstained?
could they have abstained? 	could I have been abstaining?
could you have been abstaining?
could she have been abstaining?
could we have been abstaining?
could you have been abstaining?
could they have been abstaining? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I abstain?
couldn't you abstain?
couldn't she abstain?
couldn't we abstain?
couldn't you abstain?
couldn't they abstain? 	couldn't I be abstaining?
couldn't you be abstaining?
couldn't she be abstaining?
couldn't we be abstaining?
couldn't you be abstaining?
couldn't they be abstaining? 	couldn't I have abstained?
couldn't you have abstained?
couldn't she have abstained?
couldn't we have abstained?
couldn't you have abstained?
couldn't they have abstained? 	couldn't I have been abstaining?
couldn't you have been abstaining?
couldn't she have been abstaining?
couldn't we have been abstaining?
couldn't you have been abstaining?
couldn't they have been abstaining?