could enlighten
Regular verb: enlighten - enlightened- enlightened

Affirmation 	
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I could enlighten
you could enlighten
he could enlighten
we could enlighten
you could enlighten
they could enlighten 	I could be enlightening
you could be enlightening
he could be enlightening
we could be enlightening
you could be enlightening
they could be enlightening	I could have enlightened
you could have enlightened
he could have enlightened
we could have enlightened
you could have enlightened
they could have enlightened	I could have been enlightening
you could have been enlightening
he could have been enlightening
we could have been enlightening
you could have been enlightening
they could have been enlightening	

Negation 	
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I couldn't enlighten
you couldn't enlighten
he couldn't enlighten
we couldn't enlighten
you couldn't enlighten
they couldn't enlighten 	I couldn't be enlightening
you couldn't be enlightening
he couldn't be enlightening
we couldn't be enlightening
you couldn't be enlightening
they couldn't be enlightening	I couldn't have enlightened
you couldn't have enlightened
he couldn't have enlightened
we couldn't have enlightened
you couldn't have enlightened
they couldn't have enlightened	I couldn't have been enlightening
you couldn't have been enlightening
he couldn't have been enlightening
we couldn't have been enlightening
you couldn't have been enlightening
they couldn't have been enlightening	

Interrogative form 	
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could I enlighten?
could you enlighten?
could he enlighten?
could we enlighten?
could you enlighten?
could they enlighten? 	could I be enlightening?
could you be enlightening?
could he be enlightening?
could we be enlightening?
could you be enlightening?
could they be enlightening? 	could I have enlightened?
could you have enlightened?
could he have enlightened?
could we have enlightened?
could you have enlightened?
could they have enlightened? 	could I have been enlightening?
could you have been enlightening?
could he have been enlightening?
could we have been enlightening?
could you have been enlightening?
could they have been enlightening? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I enlighten?
couldn't you enlighten?
couldn't he enlighten?
couldn't we enlighten?
couldn't you enlighten?
couldn't they enlighten? 	couldn't I be enlightening?
couldn't you be enlightening?
couldn't he be enlightening?
couldn't we be enlightening?
couldn't you be enlightening?
couldn't they be enlightening? 	couldn't I have enlightened?
couldn't you have enlightened?
couldn't he have enlightened?
couldn't we have enlightened?
couldn't you have enlightened?
couldn't they have enlightened? 	couldn't I have been enlightening?
couldn't you have been enlightening?
couldn't he have been enlightening?
couldn't we have been enlightening?
couldn't you have been enlightening?
couldn't they have been enlightening?