I could lower you could lower he could lower we could lower you could lower they could lower
V-ing form
I could be lowering you could be lowering he could be lowering we could be lowering you could be lowering they could be lowering
Perfect
I could have lowered you could have lowered he could have lowered we could have lowered you could have lowered they could have lowered
V-ing perfect
I could have been lowering you could have been lowering he could have been lowering we could have been lowering you could have been lowering they could have been lowering
Negation
Simple form
I could not lower you could not lower he could not lower we could not lower you could not lower they could not lower
V-ing form
I could not be lowering you could not be lowering he could not be lowering we could not be lowering you could not be lowering they could not be lowering
Perfect
I could not have lowered you could not have lowered he could not have lowered we could not have lowered you could not have lowered they could not have lowered
V-ing perfect
I could not have been lowering you could not have been lowering he could not have been lowering we could not have been lowering you could not have been lowering they could not have been lowering
Interrogative form
Simple form
could I lower? could you lower? could he lower? could we lower? could you lower? could they lower?
V-ing form
could I be lowering? could you be lowering? could he be lowering? could we be lowering? could you be lowering? could they be lowering?
Perfect
could I have lowered? could you have lowered? could he have lowered? could we have lowered? could you have lowered? could they have lowered?
V-ing perfect
could I have been lowering? could you have been lowering? could he have been lowering? could we have been lowering? could you have been lowering? could they have been lowering?
Interro-negative form
Simple form
could I not lower? could you not lower? could he not lower? could we not lower? could you not lower? could they not lower?
V-ing form
could I not be lowering? could you not be lowering? could he not be lowering? could we not be lowering? could you not be lowering? could they not be lowering?
Perfect
could I not have lowered? could you not have lowered? could he not have lowered? could we not have lowered? could you not have lowered? could they not have lowered?
V-ing perfect
could I not have been lowering? could you not have been lowering? could he not have been lowering? could we not have been lowering? could you not have been lowering? could they not have been lowering?