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