I could still you could still he could still we could still you could still they could still
V-ing form
I could be stilling you could be stilling he could be stilling we could be stilling you could be stilling they could be stilling
Perfect
I could have stilled you could have stilled he could have stilled we could have stilled you could have stilled they could have stilled
V-ing perfect
I could have been stilling you could have been stilling he could have been stilling we could have been stilling you could have been stilling they could have been stilling
Negation
Simple form
I could not still you could not still he could not still we could not still you could not still they could not still
V-ing form
I could not be stilling you could not be stilling he could not be stilling we could not be stilling you could not be stilling they could not be stilling
Perfect
I could not have stilled you could not have stilled he could not have stilled we could not have stilled you could not have stilled they could not have stilled
V-ing perfect
I could not have been stilling you could not have been stilling he could not have been stilling we could not have been stilling you could not have been stilling they could not have been stilling
Interrogative form
Simple form
could I still? could you still? could he still? could we still? could you still? could they still?
V-ing form
could I be stilling? could you be stilling? could he be stilling? could we be stilling? could you be stilling? could they be stilling?
Perfect
could I have stilled? could you have stilled? could he have stilled? could we have stilled? could you have stilled? could they have stilled?
V-ing perfect
could I have been stilling? could you have been stilling? could he have been stilling? could we have been stilling? could you have been stilling? could they have been stilling?
Interro-negative form
Simple form
could I not still? could you not still? could he not still? could we not still? could you not still? could they not still?
V-ing form
could I not be stilling? could you not be stilling? could he not be stilling? could we not be stilling? could you not be stilling? could they not be stilling?
Perfect
could I not have stilled? could you not have stilled? could he not have stilled? could we not have stilled? could you not have stilled? could they not have stilled?
V-ing perfect
could I not have been stilling? could you not have been stilling? could he not have been stilling? could we not have been stilling? could you not have been stilling? could they not have been stilling?