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 couldn't protest you couldn't protest he couldn't protest we couldn't protest you couldn't protest they couldn't protest
V-ing form
I couldn't be protesting you couldn't be protesting he couldn't be protesting we couldn't be protesting you couldn't be protesting they couldn't be protesting
Perfect
I couldn't have protested you couldn't have protested he couldn't have protested we couldn't have protested you couldn't have protested they couldn't have protested
V-ing perfect
I couldn't have been protesting you couldn't have been protesting he couldn't have been protesting we couldn't have been protesting you couldn't have been protesting they couldn't 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
couldn't I protest? couldn't you protest? couldn't he protest? couldn't we protest? couldn't you protest? couldn't they protest?
V-ing form
couldn't I be protesting? couldn't you be protesting? couldn't he be protesting? couldn't we be protesting? couldn't you be protesting? couldn't they be protesting?
Perfect
couldn't I have protested? couldn't you have protested? couldn't he have protested? couldn't we have protested? couldn't you have protested? couldn't they have protested?
V-ing perfect
couldn't I have been protesting? couldn't you have been protesting? couldn't he have been protesting? couldn't we have been protesting? couldn't you have been protesting? couldn't they have been protesting?