I could yell you could yell he could yell we could yell you could yell they could yell
V-ing form
I could be yelling you could be yelling he could be yelling we could be yelling you could be yelling they could be yelling
Perfect
I could have yelled you could have yelled he could have yelled we could have yelled you could have yelled they could have yelled
V-ing perfect
I could have been yelling you could have been yelling he could have been yelling we could have been yelling you could have been yelling they could have been yelling
Negation
Simple form
I could not yell you could not yell he could not yell we could not yell you could not yell they could not yell
V-ing form
I could not be yelling you could not be yelling he could not be yelling we could not be yelling you could not be yelling they could not be yelling
Perfect
I could not have yelled you could not have yelled he could not have yelled we could not have yelled you could not have yelled they could not have yelled
V-ing perfect
I could not have been yelling you could not have been yelling he could not have been yelling we could not have been yelling you could not have been yelling they could not have been yelling
Interrogative form
Simple form
could I yell? could you yell? could he yell? could we yell? could you yell? could they yell?
V-ing form
could I be yelling? could you be yelling? could he be yelling? could we be yelling? could you be yelling? could they be yelling?
Perfect
could I have yelled? could you have yelled? could he have yelled? could we have yelled? could you have yelled? could they have yelled?
V-ing perfect
could I have been yelling? could you have been yelling? could he have been yelling? could we have been yelling? could you have been yelling? could they have been yelling?
Interro-negative form
Simple form
could I not yell? could you not yell? could he not yell? could we not yell? could you not yell? could they not yell?
V-ing form
could I not be yelling? could you not be yelling? could he not be yelling? could we not be yelling? could you not be yelling? could they not be yelling?
Perfect
could I not have yelled? could you not have yelled? could he not have yelled? could we not have yelled? could you not have yelled? could they not have yelled?
V-ing perfect
could I not have been yelling? could you not have been yelling? could he not have been yelling? could we not have been yelling? could you not have been yelling? could they not have been yelling?