I could block you could block he could block we could block you could block they could block
V-ing form
I could be blocking you could be blocking he could be blocking we could be blocking you could be blocking they could be blocking
Perfect
I could have blocked you could have blocked he could have blocked we could have blocked you could have blocked they could have blocked
V-ing perfect
I could have been blocking you could have been blocking he could have been blocking we could have been blocking you could have been blocking they could have been blocking
Negation
Simple form
I could not block you could not block he could not block we could not block you could not block they could not block
V-ing form
I could not be blocking you could not be blocking he could not be blocking we could not be blocking you could not be blocking they could not be blocking
Perfect
I could not have blocked you could not have blocked he could not have blocked we could not have blocked you could not have blocked they could not have blocked
V-ing perfect
I could not have been blocking you could not have been blocking he could not have been blocking we could not have been blocking you could not have been blocking they could not have been blocking
Interrogative form
Simple form
could I block? could you block? could he block? could we block? could you block? could they block?
V-ing form
could I be blocking? could you be blocking? could he be blocking? could we be blocking? could you be blocking? could they be blocking?
Perfect
could I have blocked? could you have blocked? could he have blocked? could we have blocked? could you have blocked? could they have blocked?
V-ing perfect
could I have been blocking? could you have been blocking? could he have been blocking? could we have been blocking? could you have been blocking? could they have been blocking?
Interro-negative form
Simple form
could I not block? could you not block? could he not block? could we not block? could you not block? could they not block?
V-ing form
could I not be blocking? could you not be blocking? could he not be blocking? could we not be blocking? could you not be blocking? could they not be blocking?
Perfect
could I not have blocked? could you not have blocked? could he not have blocked? could we not have blocked? could you not have blocked? could they not have blocked?
V-ing perfect
could I not have been blocking? could you not have been blocking? could he not have been blocking? could we not have been blocking? could you not have been blocking? could they not have been blocking?