English verb conjugation
COULD DOUBT

Regular verb: doubt - doubted - doubted

Affirmation

Simple form	V-ing form
I could doubt you could doubt he could doubt we could doubt you could doubt they could doubt	I could be doubting you could be doubting he could be doubting we could be doubting you could be doubting they could be doubting
Perfect	V-ing perfect
I could have doubted you could have doubted he could have doubted we could have doubted you could have doubted they could have doubted	I could have been doubting you could have been doubting he could have been doubting we could have been doubting you could have been doubting they could have been doubting

Negation

Simple form	V-ing form
I could not doubt you could not doubt he could not doubt we could not doubt you could not doubt they could not doubt	I could not be doubting you could not be doubting he could not be doubting we could not be doubting you could not be doubting they could not be doubting
Perfect	V-ing perfect
I could not have doubted you could not have doubted he could not have doubted we could not have doubted you could not have doubted they could not have doubted	I could not have been doubting you could not have been doubting he could not have been doubting we could not have been doubting you could not have been doubting they could not have been doubting

Interrogative form

Simple form	V-ing form
could I doubt? could you doubt? could he doubt? could we doubt? could you doubt? could they doubt?	could I be doubting? could you be doubting? could he be doubting? could we be doubting? could you be doubting? could they be doubting?
Perfect	V-ing perfect
could I have doubted? could you have doubted? could he have doubted? could we have doubted? could you have doubted? could they have doubted?	could I have been doubting? could you have been doubting? could he have been doubting? could we have been doubting? could you have been doubting? could they have been doubting?

Interro-negative form

Simple form	V-ing form
could I not doubt? could you not doubt? could he not doubt? could we not doubt? could you not doubt? could they not doubt?	could I not be doubting? could you not be doubting? could he not be doubting? could we not be doubting? could you not be doubting? could they not be doubting?
Perfect	V-ing perfect
could I not have doubted? could you not have doubted? could he not have doubted? could we not have doubted? could you not have doubted? could they not have doubted?	could I not have been doubting? could you not have been doubting? could he not have been doubting? could we not have been doubting? could you not have been doubting? could they not have been doubting?