English verb conjugation
COULD VARY

Regular verb: vary - varied - varied

Affirmation

Simple form	V-ing form
I could vary you could vary she could vary we could vary you could vary they could vary	I could be varying you could be varying she could be varying we could be varying you could be varying they could be varying
Perfect	V-ing perfect
I could have varied you could have varied she could have varied we could have varied you could have varied they could have varied	I could have been varying you could have been varying she could have been varying we could have been varying you could have been varying they could have been varying

Negation

Simple form	V-ing form
I could not vary you could not vary she could not vary we could not vary you could not vary they could not vary	I could not be varying you could not be varying she could not be varying we could not be varying you could not be varying they could not be varying
Perfect	V-ing perfect
I could not have varied you could not have varied she could not have varied we could not have varied you could not have varied they could not have varied	I could not have been varying you could not have been varying she could not have been varying we could not have been varying you could not have been varying they could not have been varying

Interrogative form

Simple form	V-ing form
could I vary? could you vary? could she vary? could we vary? could you vary? could they vary?	could I be varying? could you be varying? could she be varying? could we be varying? could you be varying? could they be varying?
Perfect	V-ing perfect
could I have varied? could you have varied? could she have varied? could we have varied? could you have varied? could they have varied?	could I have been varying? could you have been varying? could she have been varying? could we have been varying? could you have been varying? could they have been varying?

Interro-negative form

Simple form	V-ing form
could I not vary? could you not vary? could she not vary? could we not vary? could you not vary? could they not vary?	could I not be varying? could you not be varying? could she not be varying? could we not be varying? could you not be varying? could they not be varying?
Perfect	V-ing perfect
could I not have varied? could you not have varied? could she not have varied? could we not have varied? could you not have varied? could they not have varied?	could I not have been varying? could you not have been varying? could she not have been varying? could we not have been varying? could you not have been varying? could they not have been varying?