I could rob you could rob he could rob we could rob you could rob they could rob
V-ing form
I could be robbing you could be robbing he could be robbing we could be robbing you could be robbing they could be robbing
Perfect
I could have robbed you could have robbed he could have robbed we could have robbed you could have robbed they could have robbed
V-ing perfect
I could have been robbing you could have been robbing he could have been robbing we could have been robbing you could have been robbing they could have been robbing
Negation
Simple form
I couldn't rob you couldn't rob he couldn't rob we couldn't rob you couldn't rob they couldn't rob
V-ing form
I couldn't be robbing you couldn't be robbing he couldn't be robbing we couldn't be robbing you couldn't be robbing they couldn't be robbing
Perfect
I couldn't have robbed you couldn't have robbed he couldn't have robbed we couldn't have robbed you couldn't have robbed they couldn't have robbed
V-ing perfect
I couldn't have been robbing you couldn't have been robbing he couldn't have been robbing we couldn't have been robbing you couldn't have been robbing they couldn't have been robbing
Interrogative form
Simple form
could I rob? could you rob? could he rob? could we rob? could you rob? could they rob?
V-ing form
could I be robbing? could you be robbing? could he be robbing? could we be robbing? could you be robbing? could they be robbing?
Perfect
could I have robbed? could you have robbed? could he have robbed? could we have robbed? could you have robbed? could they have robbed?
V-ing perfect
could I have been robbing? could you have been robbing? could he have been robbing? could we have been robbing? could you have been robbing? could they have been robbing?
Interro-negative form
Simple form
couldn't I rob? couldn't you rob? couldn't he rob? couldn't we rob? couldn't you rob? couldn't they rob?
V-ing form
couldn't I be robbing? couldn't you be robbing? couldn't he be robbing? couldn't we be robbing? couldn't you be robbing? couldn't they be robbing?
Perfect
couldn't I have robbed? couldn't you have robbed? couldn't he have robbed? couldn't we have robbed? couldn't you have robbed? couldn't they have robbed?
V-ing perfect
couldn't I have been robbing? couldn't you have been robbing? couldn't he have been robbing? couldn't we have been robbing? couldn't you have been robbing? couldn't they have been robbing?