I could hammer you could hammer he could hammer we could hammer you could hammer they could hammer
V-ing form
I could be hammering you could be hammering he could be hammering we could be hammering you could be hammering they could be hammering
Perfect
I could have hammered you could have hammered he could have hammered we could have hammered you could have hammered they could have hammered
V-ing perfect
I could have been hammering you could have been hammering he could have been hammering we could have been hammering you could have been hammering they could have been hammering
Negation
Simple form
I couldn't hammer you couldn't hammer he couldn't hammer we couldn't hammer you couldn't hammer they couldn't hammer
V-ing form
I couldn't be hammering you couldn't be hammering he couldn't be hammering we couldn't be hammering you couldn't be hammering they couldn't be hammering
Perfect
I couldn't have hammered you couldn't have hammered he couldn't have hammered we couldn't have hammered you couldn't have hammered they couldn't have hammered
V-ing perfect
I couldn't have been hammering you couldn't have been hammering he couldn't have been hammering we couldn't have been hammering you couldn't have been hammering they couldn't have been hammering
Interrogative form
Simple form
could I hammer? could you hammer? could he hammer? could we hammer? could you hammer? could they hammer?
V-ing form
could I be hammering? could you be hammering? could he be hammering? could we be hammering? could you be hammering? could they be hammering?
Perfect
could I have hammered? could you have hammered? could he have hammered? could we have hammered? could you have hammered? could they have hammered?
V-ing perfect
could I have been hammering? could you have been hammering? could he have been hammering? could we have been hammering? could you have been hammering? could they have been hammering?
Interro-negative form
Simple form
couldn't I hammer? couldn't you hammer? couldn't he hammer? couldn't we hammer? couldn't you hammer? couldn't they hammer?
V-ing form
couldn't I be hammering? couldn't you be hammering? couldn't he be hammering? couldn't we be hammering? couldn't you be hammering? couldn't they be hammering?
Perfect
couldn't I have hammered? couldn't you have hammered? couldn't he have hammered? couldn't we have hammered? couldn't you have hammered? couldn't they have hammered?
V-ing perfect
couldn't I have been hammering? couldn't you have been hammering? couldn't he have been hammering? couldn't we have been hammering? couldn't you have been hammering? couldn't they have been hammering?