could clench
Regular verb: clench - clenched- clenched

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could clench
you could clench
he could clench
we could clench
you could clench
they could clench 	I could be clenching
you could be clenching
he could be clenching
we could be clenching
you could be clenching
they could be clenching	I could have clenched
you could have clenched
he could have clenched
we could have clenched
you could have clenched
they could have clenched	I could have been clenching
you could have been clenching
he could have been clenching
we could have been clenching
you could have been clenching
they could have been clenching	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't clench
you couldn't clench
he couldn't clench
we couldn't clench
you couldn't clench
they couldn't clench 	I couldn't be clenching
you couldn't be clenching
he couldn't be clenching
we couldn't be clenching
you couldn't be clenching
they couldn't be clenching	I couldn't have clenched
you couldn't have clenched
he couldn't have clenched
we couldn't have clenched
you couldn't have clenched
they couldn't have clenched	I couldn't have been clenching
you couldn't have been clenching
he couldn't have been clenching
we couldn't have been clenching
you couldn't have been clenching
they couldn't have been clenching	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I clench?
could you clench?
could he clench?
could we clench?
could you clench?
could they clench? 	could I be clenching?
could you be clenching?
could he be clenching?
could we be clenching?
could you be clenching?
could they be clenching? 	could I have clenched?
could you have clenched?
could he have clenched?
could we have clenched?
could you have clenched?
could they have clenched? 	could I have been clenching?
could you have been clenching?
could he have been clenching?
could we have been clenching?
could you have been clenching?
could they have been clenching? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I clench?
couldn't you clench?
couldn't he clench?
couldn't we clench?
couldn't you clench?
couldn't they clench? 	couldn't I be clenching?
couldn't you be clenching?
couldn't he be clenching?
couldn't we be clenching?
couldn't you be clenching?
couldn't they be clenching? 	couldn't I have clenched?
couldn't you have clenched?
couldn't he have clenched?
couldn't we have clenched?
couldn't you have clenched?
couldn't they have clenched? 	couldn't I have been clenching?
couldn't you have been clenching?
couldn't he have been clenching?
couldn't we have been clenching?
couldn't you have been clenching?
couldn't they have been clenching?