I could protest you could protest he could protest we could protest you could protest they could protest
V-ing form
I could be protesting you could be protesting he could be protesting we could be protesting you could be protesting they could be protesting
Perfect
I could have protested you could have protested he could have protested we could have protested you could have protested they could have protested
V-ing perfect
I could have been protesting you could have been protesting he could have been protesting we could have been protesting you could have been protesting they could have been protesting
Negation
Simple form
I could not protest you could not protest he could not protest we could not protest you could not protest they could not protest
V-ing form
I could not be protesting you could not be protesting he could not be protesting we could not be protesting you could not be protesting they could not be protesting
Perfect
I could not have protested you could not have protested he could not have protested we could not have protested you could not have protested they could not have protested
V-ing perfect
I could not have been protesting you could not have been protesting he could not have been protesting we could not have been protesting you could not have been protesting they could not have been protesting
Interrogative form
Simple form
could I protest? could you protest? could he protest? could we protest? could you protest? could they protest?
V-ing form
could I be protesting? could you be protesting? could he be protesting? could we be protesting? could you be protesting? could they be protesting?
Perfect
could I have protested? could you have protested? could he have protested? could we have protested? could you have protested? could they have protested?
V-ing perfect
could I have been protesting? could you have been protesting? could he have been protesting? could we have been protesting? could you have been protesting? could they have been protesting?
Interro-negative form
Simple form
could I not protest? could you not protest? could he not protest? could we not protest? could you not protest? could they not protest?
V-ing form
could I not be protesting? could you not be protesting? could he not be protesting? could we not be protesting? could you not be protesting? could they not be protesting?
Perfect
could I not have protested? could you not have protested? could he not have protested? could we not have protested? could you not have protested? could they not have protested?
V-ing perfect
could I not have been protesting? could you not have been protesting? could he not have been protesting? could we not have been protesting? could you not have been protesting? could they not have been protesting?