could diagnose
Regular verb: diagnose - diagnosed- diagnosed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could diagnose
you could diagnose
she could diagnose
we could diagnose
you could diagnose
they could diagnose 	I could be diagnosing
you could be diagnosing
she could be diagnosing
we could be diagnosing
you could be diagnosing
they could be diagnosing	I could have diagnosed
you could have diagnosed
she 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
she 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
she 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
she 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
she 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
she 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 she diagnose?
could we diagnose?
could you diagnose?
could they diagnose? 	could I be diagnosing?
could you be diagnosing?
could she be diagnosing?
could we be diagnosing?
could you be diagnosing?
could they be diagnosing? 	could I have diagnosed?
could you have diagnosed?
could she 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 she 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 she 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 she 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 she 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 she have been diagnosing?
couldn't we have been diagnosing?
couldn't you have been diagnosing?
couldn't they have been diagnosing?