I can bob you can bob he can bob we can bob you can bob they can bob
V-ing form
I can be bobbing you can be bobbing he can be bobbing we can be bobbing you can be bobbing they can be bobbing
Perfect
I can have bobbed you can have bobbed he can have bobbed we can have bobbed you can have bobbed they can have bobbed
V-ing perfect
I can have been bobbing you can have been bobbing he can have been bobbing we can have been bobbing you can have been bobbing they can have been bobbing
Negation
Simple form
I can't bob you can't bob he can't bob we can't bob you can't bob they can't bob
V-ing form
I can't be bobbing you can't be bobbing he can't be bobbing we can't be bobbing you can't be bobbing they can't be bobbing
Perfect
I can't have bobbed you can't have bobbed he can't have bobbed we can't have bobbed you can't have bobbed they can't have bobbed
V-ing perfect
I can't have been bobbing you can't have been bobbing he can't have been bobbing we can't have been bobbing you can't have been bobbing they can't have been bobbing
Interrogative form
Simple form
can I bob? can you bob? can he bob? can we bob? can you bob? can they bob?
V-ing form
can I be bobbing? can you be bobbing? can he be bobbing? can we be bobbing? can you be bobbing? can they be bobbing?
Perfect
can I have bobbed? can you have bobbed? can he have bobbed? can we have bobbed? can you have bobbed? can they have bobbed?
V-ing perfect
can I have been bobbing? can you have been bobbing? can he have been bobbing? can we have been bobbing? can you have been bobbing? can they have been bobbing?
Interro-negative form
Simple form
can't I bob? can't you bob? can't he bob? can't we bob? can't you bob? can't they bob?
V-ing form
can't I be bobbing? can't you be bobbing? can't he be bobbing? can't we be bobbing? can't you be bobbing? can't they be bobbing?
Perfect
can't I have bobbed? can't you have bobbed? can't he have bobbed? can't we have bobbed? can't you have bobbed? can't they have bobbed?
V-ing perfect
can't I have been bobbing? can't you have been bobbing? can't he have been bobbing? can't we have been bobbing? can't you have been bobbing? can't they have been bobbing?