I could crab you could crab he could crab we could crab you could crab they could crab
V-ing form
I could be crabbing you could be crabbing he could be crabbing we could be crabbing you could be crabbing they could be crabbing
Perfect
I could have crabbed you could have crabbed he could have crabbed we could have crabbed you could have crabbed they could have crabbed
V-ing perfect
I could have been crabbing you could have been crabbing he could have been crabbing we could have been crabbing you could have been crabbing they could have been crabbing
Negation
Simple form
I could not crab you could not crab he could not crab we could not crab you could not crab they could not crab
V-ing form
I could not be crabbing you could not be crabbing he could not be crabbing we could not be crabbing you could not be crabbing they could not be crabbing
Perfect
I could not have crabbed you could not have crabbed he could not have crabbed we could not have crabbed you could not have crabbed they could not have crabbed
V-ing perfect
I could not have been crabbing you could not have been crabbing he could not have been crabbing we could not have been crabbing you could not have been crabbing they could not have been crabbing
Interrogative form
Simple form
could I crab? could you crab? could he crab? could we crab? could you crab? could they crab?
V-ing form
could I be crabbing? could you be crabbing? could he be crabbing? could we be crabbing? could you be crabbing? could they be crabbing?
Perfect
could I have crabbed? could you have crabbed? could he have crabbed? could we have crabbed? could you have crabbed? could they have crabbed?
V-ing perfect
could I have been crabbing? could you have been crabbing? could he have been crabbing? could we have been crabbing? could you have been crabbing? could they have been crabbing?
Interro-negative form
Simple form
could I not crab? could you not crab? could he not crab? could we not crab? could you not crab? could they not crab?
V-ing form
could I not be crabbing? could you not be crabbing? could he not be crabbing? could we not be crabbing? could you not be crabbing? could they not be crabbing?
Perfect
could I not have crabbed? could you not have crabbed? could he not have crabbed? could we not have crabbed? could you not have crabbed? could they not have crabbed?
V-ing perfect
could I not have been crabbing? could you not have been crabbing? could he not have been crabbing? could we not have been crabbing? could you not have been crabbing? could they not have been crabbing?