I could shriek you could shriek he could shriek we could shriek you could shriek they could shriek
V-ing form
I could be shrieking you could be shrieking he could be shrieking we could be shrieking you could be shrieking they could be shrieking
Perfect
I could have shrieked you could have shrieked he could have shrieked we could have shrieked you could have shrieked they could have shrieked
V-ing perfect
I could have been shrieking you could have been shrieking he could have been shrieking we could have been shrieking you could have been shrieking they could have been shrieking
Negation
Simple form
I could not shriek you could not shriek he could not shriek we could not shriek you could not shriek they could not shriek
V-ing form
I could not be shrieking you could not be shrieking he could not be shrieking we could not be shrieking you could not be shrieking they could not be shrieking
Perfect
I could not have shrieked you could not have shrieked he could not have shrieked we could not have shrieked you could not have shrieked they could not have shrieked
V-ing perfect
I could not have been shrieking you could not have been shrieking he could not have been shrieking we could not have been shrieking you could not have been shrieking they could not have been shrieking
Interrogative form
Simple form
could I shriek? could you shriek? could he shriek? could we shriek? could you shriek? could they shriek?
V-ing form
could I be shrieking? could you be shrieking? could he be shrieking? could we be shrieking? could you be shrieking? could they be shrieking?
Perfect
could I have shrieked? could you have shrieked? could he have shrieked? could we have shrieked? could you have shrieked? could they have shrieked?
V-ing perfect
could I have been shrieking? could you have been shrieking? could he have been shrieking? could we have been shrieking? could you have been shrieking? could they have been shrieking?
Interro-negative form
Simple form
could I not shriek? could you not shriek? could he not shriek? could we not shriek? could you not shriek? could they not shriek?
V-ing form
could I not be shrieking? could you not be shrieking? could he not be shrieking? could we not be shrieking? could you not be shrieking? could they not be shrieking?
Perfect
could I not have shrieked? could you not have shrieked? could he not have shrieked? could we not have shrieked? could you not have shrieked? could they not have shrieked?
V-ing perfect
could I not have been shrieking? could you not have been shrieking? could he not have been shrieking? could we not have been shrieking? could you not have been shrieking? could they not have been shrieking?