I can curb you can curb he can curb we can curb you can curb they can curb
V-ing form
I can be curbing you can be curbing he can be curbing we can be curbing you can be curbing they can be curbing
Perfect
I can have curbed you can have curbed he can have curbed we can have curbed you can have curbed they can have curbed
V-ing perfect
I can have been curbing you can have been curbing he can have been curbing we can have been curbing you can have been curbing they can have been curbing
Negation
Simple form
I cannot curb you cannot curb he cannot curb we cannot curb you cannot curb they cannot curb
V-ing form
I cannot be curbing you cannot be curbing he cannot be curbing we cannot be curbing you cannot be curbing they cannot be curbing
Perfect
I cannot have curbed you cannot have curbed he cannot have curbed we cannot have curbed you cannot have curbed they cannot have curbed
V-ing perfect
I cannot have been curbing you cannot have been curbing he cannot have been curbing we cannot have been curbing you cannot have been curbing they cannot have been curbing
Interrogative form
Simple form
can I curb? can you curb? can he curb? can we curb? can you curb? can they curb?
V-ing form
can I be curbing? can you be curbing? can he be curbing? can we be curbing? can you be curbing? can they be curbing?
Perfect
can I have curbed? can you have curbed? can he have curbed? can we have curbed? can you have curbed? can they have curbed?
V-ing perfect
can I have been curbing? can you have been curbing? can he have been curbing? can we have been curbing? can you have been curbing? can they have been curbing?
Interro-negative form
Simple form
can I not curb? can you not curb? can he not curb? can we not curb? can you not curb? can they not curb?
V-ing form
can I not be curbing? can you not be curbing? can he not be curbing? can we not be curbing? can you not be curbing? can they not be curbing?
Perfect
can I not have curbed? can you not have curbed? can he not have curbed? can we not have curbed? can you not have curbed? can they not have curbed?
V-ing perfect
can I not have been curbing? can you not have been curbing? can he not have been curbing? can we not have been curbing? can you not have been curbing? can they not have been curbing?