I could diagnose you could diagnose he could diagnose we could diagnose you could diagnose they could diagnose
V-ing form
I could be diagnosing you could be diagnosing he could be diagnosing we could be diagnosing you could be diagnosing they could be diagnosing
Perfect
I could have diagnosed you could have diagnosed he could have diagnosed we could have diagnosed you could have diagnosed they could have diagnosed
V-ing perfect
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
I could not diagnose you could not diagnose he could not diagnose we could not diagnose you could not diagnose they could not diagnose
V-ing form
I could not be diagnosing you could not be diagnosing he could not be diagnosing we could not be diagnosing you could not be diagnosing they could not be diagnosing
Perfect
I could not have diagnosed you could not have diagnosed he could not have diagnosed we could not have diagnosed you could not have diagnosed they could not have diagnosed
V-ing perfect
I could not have been diagnosing you could not have been diagnosing he could not have been diagnosing we could not have been diagnosing you could not have been diagnosing they could not have been diagnosing
Interrogative form
Simple form
could I diagnose? could you diagnose? could he diagnose? could we diagnose? could you diagnose? could they diagnose?
V-ing form
could I be diagnosing? could you be diagnosing? could he be diagnosing? could we be diagnosing? could you be diagnosing? could they be diagnosing?
Perfect
could I have diagnosed? could you have diagnosed? could he have diagnosed? could we have diagnosed? could you have diagnosed? could they have diagnosed?
V-ing perfect
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
could I not diagnose? could you not diagnose? could he not diagnose? could we not diagnose? could you not diagnose? could they not diagnose?
V-ing form
could I not be diagnosing? could you not be diagnosing? could he not be diagnosing? could we not be diagnosing? could you not be diagnosing? could they not be diagnosing?
Perfect
could I not have diagnosed? could you not have diagnosed? could he not have diagnosed? could we not have diagnosed? could you not have diagnosed? could they not have diagnosed?
V-ing perfect
could I not have been diagnosing? could you not have been diagnosing? could he not have been diagnosing? could we not have been diagnosing? could you not have been diagnosing? could they not have been diagnosing?