could stab
Regular verb: stab - stabbed- stabbed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could stab
you could stab
she could stab
we could stab
you could stab
they could stab 	I could be stabbing
you could be stabbing
she could be stabbing
we could be stabbing
you could be stabbing
they could be stabbing	I could have stabbed
you could have stabbed
she could have stabbed
we could have stabbed
you could have stabbed
they could have stabbed	I could have been stabbing
you could have been stabbing
she could have been stabbing
we could have been stabbing
you could have been stabbing
they could have been stabbing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't stab
you couldn't stab
she couldn't stab
we couldn't stab
you couldn't stab
they couldn't stab 	I couldn't be stabbing
you couldn't be stabbing
she couldn't be stabbing
we couldn't be stabbing
you couldn't be stabbing
they couldn't be stabbing	I couldn't have stabbed
you couldn't have stabbed
she couldn't have stabbed
we couldn't have stabbed
you couldn't have stabbed
they couldn't have stabbed	I couldn't have been stabbing
you couldn't have been stabbing
she couldn't have been stabbing
we couldn't have been stabbing
you couldn't have been stabbing
they couldn't have been stabbing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I stab?
could you stab?
could she stab?
could we stab?
could you stab?
could they stab? 	could I be stabbing?
could you be stabbing?
could she be stabbing?
could we be stabbing?
could you be stabbing?
could they be stabbing? 	could I have stabbed?
could you have stabbed?
could she have stabbed?
could we have stabbed?
could you have stabbed?
could they have stabbed? 	could I have been stabbing?
could you have been stabbing?
could she have been stabbing?
could we have been stabbing?
could you have been stabbing?
could they have been stabbing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I stab?
couldn't you stab?
couldn't she stab?
couldn't we stab?
couldn't you stab?
couldn't they stab? 	couldn't I be stabbing?
couldn't you be stabbing?
couldn't she be stabbing?
couldn't we be stabbing?
couldn't you be stabbing?
couldn't they be stabbing? 	couldn't I have stabbed?
couldn't you have stabbed?
couldn't she have stabbed?
couldn't we have stabbed?
couldn't you have stabbed?
couldn't they have stabbed? 	couldn't I have been stabbing?
couldn't you have been stabbing?
couldn't she have been stabbing?
couldn't we have been stabbing?
couldn't you have been stabbing?
couldn't they have been stabbing?