I could scale you could scale he could scale we could scale you could scale they could scale
V-ing form
I could be scaling you could be scaling he could be scaling we could be scaling you could be scaling they could be scaling
Perfect
I could have scaled you could have scaled he could have scaled we could have scaled you could have scaled they could have scaled
V-ing perfect
I could have been scaling you could have been scaling he could have been scaling we could have been scaling you could have been scaling they could have been scaling
Negation
Simple form
I could not scale you could not scale he could not scale we could not scale you could not scale they could not scale
V-ing form
I could not be scaling you could not be scaling he could not be scaling we could not be scaling you could not be scaling they could not be scaling
Perfect
I could not have scaled you could not have scaled he could not have scaled we could not have scaled you could not have scaled they could not have scaled
V-ing perfect
I could not have been scaling you could not have been scaling he could not have been scaling we could not have been scaling you could not have been scaling they could not have been scaling
Interrogative form
Simple form
could I scale? could you scale? could he scale? could we scale? could you scale? could they scale?
V-ing form
could I be scaling? could you be scaling? could he be scaling? could we be scaling? could you be scaling? could they be scaling?
Perfect
could I have scaled? could you have scaled? could he have scaled? could we have scaled? could you have scaled? could they have scaled?
V-ing perfect
could I have been scaling? could you have been scaling? could he have been scaling? could we have been scaling? could you have been scaling? could they have been scaling?
Interro-negative form
Simple form
could I not scale? could you not scale? could he not scale? could we not scale? could you not scale? could they not scale?
V-ing form
could I not be scaling? could you not be scaling? could he not be scaling? could we not be scaling? could you not be scaling? could they not be scaling?
Perfect
could I not have scaled? could you not have scaled? could he not have scaled? could we not have scaled? could you not have scaled? could they not have scaled?
V-ing perfect
could I not have been scaling? could you not have been scaling? could he not have been scaling? could we not have been scaling? could you not have been scaling? could they not have been scaling?