I can down you can down she can down we can down you can down they can down
V-ing form
I can be downing you can be downing she can be downing we can be downing you can be downing they can be downing
Perfect
I can have downed you can have downed she can have downed we can have downed you can have downed they can have downed
V-ing perfect
I can have been downing you can have been downing she can have been downing we can have been downing you can have been downing they can have been downing
Negation
Simple form
I cannot down you cannot down she cannot down we cannot down you cannot down they cannot down
V-ing form
I cannot be downing you cannot be downing she cannot be downing we cannot be downing you cannot be downing they cannot be downing
Perfect
I cannot have downed you cannot have downed she cannot have downed we cannot have downed you cannot have downed they cannot have downed
V-ing perfect
I cannot have been downing you cannot have been downing she cannot have been downing we cannot have been downing you cannot have been downing they cannot have been downing
Interrogative form
Simple form
can I down? can you down? can she down? can we down? can you down? can they down?
V-ing form
can I be downing? can you be downing? can she be downing? can we be downing? can you be downing? can they be downing?
Perfect
can I have downed? can you have downed? can she have downed? can we have downed? can you have downed? can they have downed?
V-ing perfect
can I have been downing? can you have been downing? can she have been downing? can we have been downing? can you have been downing? can they have been downing?
Interro-negative form
Simple form
can I not down? can you not down? can she not down? can we not down? can you not down? can they not down?
V-ing form
can I not be downing? can you not be downing? can she not be downing? can we not be downing? can you not be downing? can they not be downing?
Perfect
can I not have downed? can you not have downed? can she not have downed? can we not have downed? can you not have downed? can they not have downed?
V-ing perfect
can I not have been downing? can you not have been downing? can she not have been downing? can we not have been downing? can you not have been downing? can they not have been downing?