I could backstroke you could backstroke he could backstroke we could backstroke you could backstroke they could backstroke
V-ing form
I could be backstroking you could be backstroking he could be backstroking we could be backstroking you could be backstroking they could be backstroking
Perfect
I could have backstroked you could have backstroked he could have backstroked we could have backstroked you could have backstroked they could have backstroked
V-ing perfect
I could have been backstroking you could have been backstroking he could have been backstroking we could have been backstroking you could have been backstroking they could have been backstroking
Negation
Simple form
I could not backstroke you could not backstroke he could not backstroke we could not backstroke you could not backstroke they could not backstroke
V-ing form
I could not be backstroking you could not be backstroking he could not be backstroking we could not be backstroking you could not be backstroking they could not be backstroking
Perfect
I could not have backstroked you could not have backstroked he could not have backstroked we could not have backstroked you could not have backstroked they could not have backstroked
V-ing perfect
I could not have been backstroking you could not have been backstroking he could not have been backstroking we could not have been backstroking you could not have been backstroking they could not have been backstroking
Interrogative form
Simple form
could I backstroke? could you backstroke? could he backstroke? could we backstroke? could you backstroke? could they backstroke?
V-ing form
could I be backstroking? could you be backstroking? could he be backstroking? could we be backstroking? could you be backstroking? could they be backstroking?
Perfect
could I have backstroked? could you have backstroked? could he have backstroked? could we have backstroked? could you have backstroked? could they have backstroked?
V-ing perfect
could I have been backstroking? could you have been backstroking? could he have been backstroking? could we have been backstroking? could you have been backstroking? could they have been backstroking?
Interro-negative form
Simple form
could I not backstroke? could you not backstroke? could he not backstroke? could we not backstroke? could you not backstroke? could they not backstroke?
V-ing form
could I not be backstroking? could you not be backstroking? could he not be backstroking? could we not be backstroking? could you not be backstroking? could they not be backstroking?
Perfect
could I not have backstroked? could you not have backstroked? could he not have backstroked? could we not have backstroked? could you not have backstroked? could they not have backstroked?
V-ing perfect
could I not have been backstroking? could you not have been backstroking? could he not have been backstroking? could we not have been backstroking? could you not have been backstroking? could they not have been backstroking?