could diagnose
Regular verb: diagnose - diagnosed- diagnosed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could diagnose
you could diagnose
he could diagnose
we could diagnose
you could diagnose
they could diagnose 	I could be diagnosing
you could be diagnosing
he could be diagnosing
we could be diagnosing
you could be diagnosing
they could be diagnosing	I could have diagnosed
you could have diagnosed
he could have diagnosed
we could have diagnosed
you could have diagnosed
they could have diagnosed	I could have been diagnosing
you could have been diagnosing
he could have been diagnosing
we could have been diagnosing
you could have been diagnosing
they could have been diagnosing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't diagnose
you couldn't diagnose
he couldn't diagnose
we couldn't diagnose
you couldn't diagnose
they couldn't diagnose 	I couldn't be diagnosing
you couldn't be diagnosing
he couldn't be diagnosing
we couldn't be diagnosing
you couldn't be diagnosing
they couldn't be diagnosing	I couldn't have diagnosed
you couldn't have diagnosed
he couldn't have diagnosed
we couldn't have diagnosed
you couldn't have diagnosed
they couldn't have diagnosed	I couldn't have been diagnosing
you couldn't have been diagnosing
he couldn't have been diagnosing
we couldn't have been diagnosing
you couldn't have been diagnosing
they couldn't have been diagnosing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I diagnose?
could you diagnose?
could he diagnose?
could we diagnose?
could you diagnose?
could they diagnose? 	could I be diagnosing?
could you be diagnosing?
could he be diagnosing?
could we be diagnosing?
could you be diagnosing?
could they be diagnosing? 	could I have diagnosed?
could you have diagnosed?
could he have diagnosed?
could we have diagnosed?
could you have diagnosed?
could they have diagnosed? 	could I have been diagnosing?
could you have been diagnosing?
could he have been diagnosing?
could we have been diagnosing?
could you have been diagnosing?
could they have been diagnosing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I diagnose?
couldn't you diagnose?
couldn't he diagnose?
couldn't we diagnose?
couldn't you diagnose?
couldn't they diagnose? 	couldn't I be diagnosing?
couldn't you be diagnosing?
couldn't he be diagnosing?
couldn't we be diagnosing?
couldn't you be diagnosing?
couldn't they be diagnosing? 	couldn't I have diagnosed?
couldn't you have diagnosed?
couldn't he have diagnosed?
couldn't we have diagnosed?
couldn't you have diagnosed?
couldn't they have diagnosed? 	couldn't I have been diagnosing?
couldn't you have been diagnosing?
couldn't he have been diagnosing?
couldn't we have been diagnosing?
couldn't you have been diagnosing?
couldn't they have been diagnosing?