could intervene
Regular verb: intervene - intervened- intervened

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could intervene
you could intervene
she could intervene
we could intervene
you could intervene
they could intervene 	I could be intervening
you could be intervening
she could be intervening
we could be intervening
you could be intervening
they could be intervening	I could have intervened
you could have intervened
she could have intervened
we could have intervened
you could have intervened
they could have intervened	I could have been intervening
you could have been intervening
she could have been intervening
we could have been intervening
you could have been intervening
they could have been intervening	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not intervene
you could not intervene
she could not intervene
we could not intervene
you could not intervene
they could not intervene 	I could not be intervening
you could not be intervening
she could not be intervening
we could not be intervening
you could not be intervening
they could not be intervening	I could not have intervened
you could not have intervened
she could not have intervened
we could not have intervened
you could not have intervened
they could not have intervened	I could not have been intervening
you could not have been intervening
she could not have been intervening
we could not have been intervening
you could not have been intervening
they could not have been intervening	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I intervene?
could you intervene?
could she intervene?
could we intervene?
could you intervene?
could they intervene? 	could I be intervening?
could you be intervening?
could she be intervening?
could we be intervening?
could you be intervening?
could they be intervening? 	could I have intervened?
could you have intervened?
could she have intervened?
could we have intervened?
could you have intervened?
could they have intervened? 	could I have been intervening?
could you have been intervening?
could she have been intervening?
could we have been intervening?
could you have been intervening?
could they have been intervening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not intervene?
could you not intervene?
could she not intervene?
could we not intervene?
could you not intervene?
could they not intervene? 	could I not be intervening?
could you not be intervening?
could she not be intervening?
could we not be intervening?
could you not be intervening?
could they not be intervening? 	could I not have intervened?
could you not have intervened?
could she not have intervened?
could we not have intervened?
could you not have intervened?
could they not have intervened? 	could I not have been intervening?
could you not have been intervening?
could she not have been intervening?
could we not have been intervening?
could you not have been intervening?
could they not have been intervening?