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 couldn't block you couldn't block he couldn't block we couldn't block you couldn't block they couldn't block
V-ing form
I couldn't be blocking you couldn't be blocking he couldn't be blocking we couldn't be blocking you couldn't be blocking they couldn't be blocking
Perfect
I couldn't have blocked you couldn't have blocked he couldn't have blocked we couldn't have blocked you couldn't have blocked they couldn't have blocked
V-ing perfect
I couldn't have been blocking you couldn't have been blocking he couldn't have been blocking we couldn't have been blocking you couldn't have been blocking they couldn't 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
couldn't I block? couldn't you block? couldn't he block? couldn't we block? couldn't you block? couldn't they block?
V-ing form
couldn't I be blocking? couldn't you be blocking? couldn't he be blocking? couldn't we be blocking? couldn't you be blocking? couldn't they be blocking?
Perfect
couldn't I have blocked? couldn't you have blocked? couldn't he have blocked? couldn't we have blocked? couldn't you have blocked? couldn't they have blocked?
V-ing perfect
couldn't I have been blocking? couldn't you have been blocking? couldn't he have been blocking? couldn't we have been blocking? couldn't you have been blocking? couldn't they have been blocking?