I could unmask you could unmask he could unmask we could unmask you could unmask they could unmask
V-ing form
I could be unmasking you could be unmasking he could be unmasking we could be unmasking you could be unmasking they could be unmasking
Perfect
I could have unmasked you could have unmasked he could have unmasked we could have unmasked you could have unmasked they could have unmasked
V-ing perfect
I could have been unmasking you could have been unmasking he could have been unmasking we could have been unmasking you could have been unmasking they could have been unmasking
Negation
Simple form
I could not unmask you could not unmask he could not unmask we could not unmask you could not unmask they could not unmask
V-ing form
I could not be unmasking you could not be unmasking he could not be unmasking we could not be unmasking you could not be unmasking they could not be unmasking
Perfect
I could not have unmasked you could not have unmasked he could not have unmasked we could not have unmasked you could not have unmasked they could not have unmasked
V-ing perfect
I could not have been unmasking you could not have been unmasking he could not have been unmasking we could not have been unmasking you could not have been unmasking they could not have been unmasking
Interrogative form
Simple form
could I unmask? could you unmask? could he unmask? could we unmask? could you unmask? could they unmask?
V-ing form
could I be unmasking? could you be unmasking? could he be unmasking? could we be unmasking? could you be unmasking? could they be unmasking?
Perfect
could I have unmasked? could you have unmasked? could he have unmasked? could we have unmasked? could you have unmasked? could they have unmasked?
V-ing perfect
could I have been unmasking? could you have been unmasking? could he have been unmasking? could we have been unmasking? could you have been unmasking? could they have been unmasking?
Interro-negative form
Simple form
could I not unmask? could you not unmask? could he not unmask? could we not unmask? could you not unmask? could they not unmask?
V-ing form
could I not be unmasking? could you not be unmasking? could he not be unmasking? could we not be unmasking? could you not be unmasking? could they not be unmasking?
Perfect
could I not have unmasked? could you not have unmasked? could he not have unmasked? could we not have unmasked? could you not have unmasked? could they not have unmasked?
V-ing perfect
could I not have been unmasking? could you not have been unmasking? could he not have been unmasking? could we not have been unmasking? could you not have been unmasking? could they not have been unmasking?