English verb conjugation
CAN CERTIFY

Regular verb: certify - certified - certified

Affirmation

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

Negation

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

Interrogative form

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

Interro-negative form

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