could trephine
Regular verb: trephine - trephined- trephined

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could trephine
you could trephine
he could trephine
we could trephine
you could trephine
they could trephine 	I could be trephining
you could be trephining
he could be trephining
we could be trephining
you could be trephining
they could be trephining	I could have trephined
you could have trephined
he could have trephined
we could have trephined
you could have trephined
they could have trephined	I could have been trephining
you could have been trephining
he could have been trephining
we could have been trephining
you could have been trephining
they could have been trephining	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't trephine
you couldn't trephine
he couldn't trephine
we couldn't trephine
you couldn't trephine
they couldn't trephine 	I couldn't be trephining
you couldn't be trephining
he couldn't be trephining
we couldn't be trephining
you couldn't be trephining
they couldn't be trephining	I couldn't have trephined
you couldn't have trephined
he couldn't have trephined
we couldn't have trephined
you couldn't have trephined
they couldn't have trephined	I couldn't have been trephining
you couldn't have been trephining
he couldn't have been trephining
we couldn't have been trephining
you couldn't have been trephining
they couldn't have been trephining	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I trephine?
could you trephine?
could he trephine?
could we trephine?
could you trephine?
could they trephine? 	could I be trephining?
could you be trephining?
could he be trephining?
could we be trephining?
could you be trephining?
could they be trephining? 	could I have trephined?
could you have trephined?
could he have trephined?
could we have trephined?
could you have trephined?
could they have trephined? 	could I have been trephining?
could you have been trephining?
could he have been trephining?
could we have been trephining?
could you have been trephining?
could they have been trephining? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I trephine?
couldn't you trephine?
couldn't he trephine?
couldn't we trephine?
couldn't you trephine?
couldn't they trephine? 	couldn't I be trephining?
couldn't you be trephining?
couldn't he be trephining?
couldn't we be trephining?
couldn't you be trephining?
couldn't they be trephining? 	couldn't I have trephined?
couldn't you have trephined?
couldn't he have trephined?
couldn't we have trephined?
couldn't you have trephined?
couldn't they have trephined? 	couldn't I have been trephining?
couldn't you have been trephining?
couldn't he have been trephining?
couldn't we have been trephining?
couldn't you have been trephining?
couldn't they have been trephining?