could succumb
Regular verb: succumb - succumbed- succumbed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could succumb
you could succumb
he could succumb
we could succumb
you could succumb
they could succumb 	I could be succumbing
you could be succumbing
he could be succumbing
we could be succumbing
you could be succumbing
they could be succumbing	I could have succumbed
you could have succumbed
he could have succumbed
we could have succumbed
you could have succumbed
they could have succumbed	I could have been succumbing
you could have been succumbing
he could have been succumbing
we could have been succumbing
you could have been succumbing
they could have been succumbing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't succumb
you couldn't succumb
he couldn't succumb
we couldn't succumb
you couldn't succumb
they couldn't succumb 	I couldn't be succumbing
you couldn't be succumbing
he couldn't be succumbing
we couldn't be succumbing
you couldn't be succumbing
they couldn't be succumbing	I couldn't have succumbed
you couldn't have succumbed
he couldn't have succumbed
we couldn't have succumbed
you couldn't have succumbed
they couldn't have succumbed	I couldn't have been succumbing
you couldn't have been succumbing
he couldn't have been succumbing
we couldn't have been succumbing
you couldn't have been succumbing
they couldn't have been succumbing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I succumb?
could you succumb?
could he succumb?
could we succumb?
could you succumb?
could they succumb? 	could I be succumbing?
could you be succumbing?
could he be succumbing?
could we be succumbing?
could you be succumbing?
could they be succumbing? 	could I have succumbed?
could you have succumbed?
could he have succumbed?
could we have succumbed?
could you have succumbed?
could they have succumbed? 	could I have been succumbing?
could you have been succumbing?
could he have been succumbing?
could we have been succumbing?
could you have been succumbing?
could they have been succumbing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I succumb?
couldn't you succumb?
couldn't he succumb?
couldn't we succumb?
couldn't you succumb?
couldn't they succumb? 	couldn't I be succumbing?
couldn't you be succumbing?
couldn't he be succumbing?
couldn't we be succumbing?
couldn't you be succumbing?
couldn't they be succumbing? 	couldn't I have succumbed?
couldn't you have succumbed?
couldn't he have succumbed?
couldn't we have succumbed?
couldn't you have succumbed?
couldn't they have succumbed? 	couldn't I have been succumbing?
couldn't you have been succumbing?
couldn't he have been succumbing?
couldn't we have been succumbing?
couldn't you have been succumbing?
couldn't they have been succumbing?