English verb conjugation
COULD CERTIFY

Regular verb: certify - certified - certified

Affirmation

Simple form	V-ing form
I could certify you could certify she could certify we could certify you could certify they could certify	I could be certifying you could be certifying she could be certifying we could be certifying you could be certifying they could be certifying
Perfect	V-ing perfect
I could have certified you could have certified she could have certified we could have certified you could have certified they could have certified	I could have been certifying you could have been certifying she could have been certifying we could have been certifying you could have been certifying they could have been certifying

Negation

Simple form	V-ing form
I couldn't certify you couldn't certify she couldn't certify we couldn't certify you couldn't certify they couldn't certify	I couldn't be certifying you couldn't be certifying she couldn't be certifying we couldn't be certifying you couldn't be certifying they couldn't be certifying
Perfect	V-ing perfect
I couldn't have certified you couldn't have certified she couldn't have certified we couldn't have certified you couldn't have certified they couldn't have certified	I couldn't have been certifying you couldn't have been certifying she couldn't have been certifying we couldn't have been certifying you couldn't have been certifying they couldn't have been certifying

Interrogative form

Simple form	V-ing form
could I certify? could you certify? could she certify? could we certify? could you certify? could they certify?	could I be certifying? could you be certifying? could she be certifying? could we be certifying? could you be certifying? could they be certifying?
Perfect	V-ing perfect
could I have certified? could you have certified? could she have certified? could we have certified? could you have certified? could they have certified?	could I have been certifying? could you have been certifying? could she have been certifying? could we have been certifying? could you have been certifying? could they have been certifying?

Interro-negative form

Simple form	V-ing form
couldn't I certify? couldn't you certify? couldn't she certify? couldn't we certify? couldn't you certify? couldn't they certify?	couldn't I be certifying? couldn't you be certifying? couldn't she be certifying? couldn't we be certifying? couldn't you be certifying? couldn't they be certifying?
Perfect	V-ing perfect
couldn't I have certified? couldn't you have certified? couldn't she have certified? couldn't we have certified? couldn't you have certified? couldn't they have certified?	couldn't I have been certifying? couldn't you have been certifying? couldn't she have been certifying? couldn't we have been certifying? couldn't you have been certifying? couldn't they have been certifying?