could tarnish
Regular verb: tarnish - tarnished- tarnished

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could tarnish
you could tarnish
he could tarnish
we could tarnish
you could tarnish
they could tarnish 	I could be tarnishing
you could be tarnishing
he could be tarnishing
we could be tarnishing
you could be tarnishing
they could be tarnishing	I could have tarnished
you could have tarnished
he could have tarnished
we could have tarnished
you could have tarnished
they could have tarnished	I could have been tarnishing
you could have been tarnishing
he could have been tarnishing
we could have been tarnishing
you could have been tarnishing
they could have been tarnishing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't tarnish
you couldn't tarnish
he couldn't tarnish
we couldn't tarnish
you couldn't tarnish
they couldn't tarnish 	I couldn't be tarnishing
you couldn't be tarnishing
he couldn't be tarnishing
we couldn't be tarnishing
you couldn't be tarnishing
they couldn't be tarnishing	I couldn't have tarnished
you couldn't have tarnished
he couldn't have tarnished
we couldn't have tarnished
you couldn't have tarnished
they couldn't have tarnished	I couldn't have been tarnishing
you couldn't have been tarnishing
he couldn't have been tarnishing
we couldn't have been tarnishing
you couldn't have been tarnishing
they couldn't have been tarnishing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I tarnish?
could you tarnish?
could he tarnish?
could we tarnish?
could you tarnish?
could they tarnish? 	could I be tarnishing?
could you be tarnishing?
could he be tarnishing?
could we be tarnishing?
could you be tarnishing?
could they be tarnishing? 	could I have tarnished?
could you have tarnished?
could he have tarnished?
could we have tarnished?
could you have tarnished?
could they have tarnished? 	could I have been tarnishing?
could you have been tarnishing?
could he have been tarnishing?
could we have been tarnishing?
could you have been tarnishing?
could they have been tarnishing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I tarnish?
couldn't you tarnish?
couldn't he tarnish?
couldn't we tarnish?
couldn't you tarnish?
couldn't they tarnish? 	couldn't I be tarnishing?
couldn't you be tarnishing?
couldn't he be tarnishing?
couldn't we be tarnishing?
couldn't you be tarnishing?
couldn't they be tarnishing? 	couldn't I have tarnished?
couldn't you have tarnished?
couldn't he have tarnished?
couldn't we have tarnished?
couldn't you have tarnished?
couldn't they have tarnished? 	couldn't I have been tarnishing?
couldn't you have been tarnishing?
couldn't he have been tarnishing?
couldn't we have been tarnishing?
couldn't you have been tarnishing?
couldn't they have been tarnishing?