could clench
Regular verb: clench - clenched- clenched

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could clench
you could clench
she could clench
we could clench
you could clench
they could clench 	I could be clenching
you could be clenching
she could be clenching
we could be clenching
you could be clenching
they could be clenching	I could have clenched
you could have clenched
she 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
she 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 could not clench
you could not clench
she could not clench
we could not clench
you could not clench
they could not clench 	I could not be clenching
you could not be clenching
she could not be clenching
we could not be clenching
you could not be clenching
they could not be clenching	I could not have clenched
you could not have clenched
she could not have clenched
we could not have clenched
you could not have clenched
they could not have clenched	I could not have been clenching
you could not have been clenching
she could not have been clenching
we could not have been clenching
you could not have been clenching
they could not have been clenching	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I clench?
could you clench?
could she clench?
could we clench?
could you clench?
could they clench? 	could I be clenching?
could you be clenching?
could she be clenching?
could we be clenching?
could you be clenching?
could they be clenching? 	could I have clenched?
could you have clenched?
could she 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 she 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 	
could I not clench?
could you not clench?
could she not clench?
could we not clench?
could you not clench?
could they not clench? 	could I not be clenching?
could you not be clenching?
could she not be clenching?
could we not be clenching?
could you not be clenching?
could they not be clenching? 	could I not have clenched?
could you not have clenched?
could she not have clenched?
could we not have clenched?
could you not have clenched?
could they not have clenched? 	could I not have been clenching?
could you not have been clenching?
could she not have been clenching?
could we not have been clenching?
could you not have been clenching?
could they not have been clenching?