could stifle
Regular verb: stifle - stifled- stifled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could stifle
you could stifle
she could stifle
we could stifle
you could stifle
they could stifle 	I could be stifling
you could be stifling
she could be stifling
we could be stifling
you could be stifling
they could be stifling	I could have stifled
you could have stifled
she could have stifled
we could have stifled
you could have stifled
they could have stifled	I could have been stifling
you could have been stifling
she could have been stifling
we could have been stifling
you could have been stifling
they could have been stifling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't stifle
you couldn't stifle
she couldn't stifle
we couldn't stifle
you couldn't stifle
they couldn't stifle 	I couldn't be stifling
you couldn't be stifling
she couldn't be stifling
we couldn't be stifling
you couldn't be stifling
they couldn't be stifling	I couldn't have stifled
you couldn't have stifled
she couldn't have stifled
we couldn't have stifled
you couldn't have stifled
they couldn't have stifled	I couldn't have been stifling
you couldn't have been stifling
she couldn't have been stifling
we couldn't have been stifling
you couldn't have been stifling
they couldn't have been stifling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I stifle?
could you stifle?
could she stifle?
could we stifle?
could you stifle?
could they stifle? 	could I be stifling?
could you be stifling?
could she be stifling?
could we be stifling?
could you be stifling?
could they be stifling? 	could I have stifled?
could you have stifled?
could she have stifled?
could we have stifled?
could you have stifled?
could they have stifled? 	could I have been stifling?
could you have been stifling?
could she have been stifling?
could we have been stifling?
could you have been stifling?
could they have been stifling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I stifle?
couldn't you stifle?
couldn't she stifle?
couldn't we stifle?
couldn't you stifle?
couldn't they stifle? 	couldn't I be stifling?
couldn't you be stifling?
couldn't she be stifling?
couldn't we be stifling?
couldn't you be stifling?
couldn't they be stifling? 	couldn't I have stifled?
couldn't you have stifled?
couldn't she have stifled?
couldn't we have stifled?
couldn't you have stifled?
couldn't they have stifled? 	couldn't I have been stifling?
couldn't you have been stifling?
couldn't she have been stifling?
couldn't we have been stifling?
couldn't you have been stifling?
couldn't they have been stifling?