I could scrub you could scrub he could scrub we could scrub you could scrub they could scrub
V-ing form
I could be scrubbing you could be scrubbing he could be scrubbing we could be scrubbing you could be scrubbing they could be scrubbing
Perfect
I could have scrubbed you could have scrubbed he could have scrubbed we could have scrubbed you could have scrubbed they could have scrubbed
V-ing perfect
I could have been scrubbing you could have been scrubbing he could have been scrubbing we could have been scrubbing you could have been scrubbing they could have been scrubbing
Negation
Simple form
I could not scrub you could not scrub he could not scrub we could not scrub you could not scrub they could not scrub
V-ing form
I could not be scrubbing you could not be scrubbing he could not be scrubbing we could not be scrubbing you could not be scrubbing they could not be scrubbing
Perfect
I could not have scrubbed you could not have scrubbed he could not have scrubbed we could not have scrubbed you could not have scrubbed they could not have scrubbed
V-ing perfect
I could not have been scrubbing you could not have been scrubbing he could not have been scrubbing we could not have been scrubbing you could not have been scrubbing they could not have been scrubbing
Interrogative form
Simple form
could I scrub? could you scrub? could he scrub? could we scrub? could you scrub? could they scrub?
V-ing form
could I be scrubbing? could you be scrubbing? could he be scrubbing? could we be scrubbing? could you be scrubbing? could they be scrubbing?
Perfect
could I have scrubbed? could you have scrubbed? could he have scrubbed? could we have scrubbed? could you have scrubbed? could they have scrubbed?
V-ing perfect
could I have been scrubbing? could you have been scrubbing? could he have been scrubbing? could we have been scrubbing? could you have been scrubbing? could they have been scrubbing?
Interro-negative form
Simple form
could I not scrub? could you not scrub? could he not scrub? could we not scrub? could you not scrub? could they not scrub?
V-ing form
could I not be scrubbing? could you not be scrubbing? could he not be scrubbing? could we not be scrubbing? could you not be scrubbing? could they not be scrubbing?
Perfect
could I not have scrubbed? could you not have scrubbed? could he not have scrubbed? could we not have scrubbed? could you not have scrubbed? could they not have scrubbed?
V-ing perfect
could I not have been scrubbing? could you not have been scrubbing? could he not have been scrubbing? could we not have been scrubbing? could you not have been scrubbing? could they not have been scrubbing?