I could stain you could stain he could stain we could stain you could stain they could stain
V-ing form
I could be staining you could be staining he could be staining we could be staining you could be staining they could be staining
Perfect
I could have stained you could have stained he could have stained we could have stained you could have stained they could have stained
V-ing perfect
I could have been staining you could have been staining he could have been staining we could have been staining you could have been staining they could have been staining
Negation
Simple form
I could not stain you could not stain he could not stain we could not stain you could not stain they could not stain
V-ing form
I could not be staining you could not be staining he could not be staining we could not be staining you could not be staining they could not be staining
Perfect
I could not have stained you could not have stained he could not have stained we could not have stained you could not have stained they could not have stained
V-ing perfect
I could not have been staining you could not have been staining he could not have been staining we could not have been staining you could not have been staining they could not have been staining
Interrogative form
Simple form
could I stain? could you stain? could he stain? could we stain? could you stain? could they stain?
V-ing form
could I be staining? could you be staining? could he be staining? could we be staining? could you be staining? could they be staining?
Perfect
could I have stained? could you have stained? could he have stained? could we have stained? could you have stained? could they have stained?
V-ing perfect
could I have been staining? could you have been staining? could he have been staining? could we have been staining? could you have been staining? could they have been staining?
Interro-negative form
Simple form
could I not stain? could you not stain? could he not stain? could we not stain? could you not stain? could they not stain?
V-ing form
could I not be staining? could you not be staining? could he not be staining? could we not be staining? could you not be staining? could they not be staining?
Perfect
could I not have stained? could you not have stained? could he not have stained? could we not have stained? could you not have stained? could they not have stained?
V-ing perfect
could I not have been staining? could you not have been staining? could he not have been staining? could we not have been staining? could you not have been staining? could they not have been staining?