I could shell you could shell she could shell we could shell you could shell they could shell
V-ing form
I could be shelling you could be shelling she could be shelling we could be shelling you could be shelling they could be shelling
Perfect
I could have shelled you could have shelled she could have shelled we could have shelled you could have shelled they could have shelled
V-ing perfect
I could have been shelling you could have been shelling she could have been shelling we could have been shelling you could have been shelling they could have been shelling
Negation
Simple form
I could not shell you could not shell she could not shell we could not shell you could not shell they could not shell
V-ing form
I could not be shelling you could not be shelling she could not be shelling we could not be shelling you could not be shelling they could not be shelling
Perfect
I could not have shelled you could not have shelled she could not have shelled we could not have shelled you could not have shelled they could not have shelled
V-ing perfect
I could not have been shelling you could not have been shelling she could not have been shelling we could not have been shelling you could not have been shelling they could not have been shelling
Interrogative form
Simple form
could I shell? could you shell? could she shell? could we shell? could you shell? could they shell?
V-ing form
could I be shelling? could you be shelling? could she be shelling? could we be shelling? could you be shelling? could they be shelling?
Perfect
could I have shelled? could you have shelled? could she have shelled? could we have shelled? could you have shelled? could they have shelled?
V-ing perfect
could I have been shelling? could you have been shelling? could she have been shelling? could we have been shelling? could you have been shelling? could they have been shelling?
Interro-negative form
Simple form
could I not shell? could you not shell? could she not shell? could we not shell? could you not shell? could they not shell?
V-ing form
could I not be shelling? could you not be shelling? could she not be shelling? could we not be shelling? could you not be shelling? could they not be shelling?
Perfect
could I not have shelled? could you not have shelled? could she not have shelled? could we not have shelled? could you not have shelled? could they not have shelled?
V-ing perfect
could I not have been shelling? could you not have been shelling? could she not have been shelling? could we not have been shelling? could you not have been shelling? could they not have been shelling?