I can sign you can sign he can sign we can sign you can sign they can sign
V-ing form
I can be signing you can be signing he can be signing we can be signing you can be signing they can be signing
Perfect
I can have signed you can have signed he can have signed we can have signed you can have signed they can have signed
V-ing perfect
I can have been signing you can have been signing he can have been signing we can have been signing you can have been signing they can have been signing
Negation
Simple form
I cannot sign you cannot sign he cannot sign we cannot sign you cannot sign they cannot sign
V-ing form
I cannot be signing you cannot be signing he cannot be signing we cannot be signing you cannot be signing they cannot be signing
Perfect
I cannot have signed you cannot have signed he cannot have signed we cannot have signed you cannot have signed they cannot have signed
V-ing perfect
I cannot have been signing you cannot have been signing he cannot have been signing we cannot have been signing you cannot have been signing they cannot have been signing
Interrogative form
Simple form
can I sign? can you sign? can he sign? can we sign? can you sign? can they sign?
V-ing form
can I be signing? can you be signing? can he be signing? can we be signing? can you be signing? can they be signing?
Perfect
can I have signed? can you have signed? can he have signed? can we have signed? can you have signed? can they have signed?
V-ing perfect
can I have been signing? can you have been signing? can he have been signing? can we have been signing? can you have been signing? can they have been signing?
Interro-negative form
Simple form
can I not sign? can you not sign? can he not sign? can we not sign? can you not sign? can they not sign?
V-ing form
can I not be signing? can you not be signing? can he not be signing? can we not be signing? can you not be signing? can they not be signing?
Perfect
can I not have signed? can you not have signed? can he not have signed? can we not have signed? can you not have signed? can they not have signed?
V-ing perfect
can I not have been signing? can you not have been signing? can he not have been signing? can we not have been signing? can you not have been signing? can they not have been signing?