I could sob you could sob he could sob we could sob you could sob they could sob
V-ing form
I could be sobbing you could be sobbing he could be sobbing we could be sobbing you could be sobbing they could be sobbing
Perfect
I could have sobbed you could have sobbed he could have sobbed we could have sobbed you could have sobbed they could have sobbed
V-ing perfect
I could have been sobbing you could have been sobbing he could have been sobbing we could have been sobbing you could have been sobbing they could have been sobbing
Negation
Simple form
I could not sob you could not sob he could not sob we could not sob you could not sob they could not sob
V-ing form
I could not be sobbing you could not be sobbing he could not be sobbing we could not be sobbing you could not be sobbing they could not be sobbing
Perfect
I could not have sobbed you could not have sobbed he could not have sobbed we could not have sobbed you could not have sobbed they could not have sobbed
V-ing perfect
I could not have been sobbing you could not have been sobbing he could not have been sobbing we could not have been sobbing you could not have been sobbing they could not have been sobbing
Interrogative form
Simple form
could I sob? could you sob? could he sob? could we sob? could you sob? could they sob?
V-ing form
could I be sobbing? could you be sobbing? could he be sobbing? could we be sobbing? could you be sobbing? could they be sobbing?
Perfect
could I have sobbed? could you have sobbed? could he have sobbed? could we have sobbed? could you have sobbed? could they have sobbed?
V-ing perfect
could I have been sobbing? could you have been sobbing? could he have been sobbing? could we have been sobbing? could you have been sobbing? could they have been sobbing?
Interro-negative form
Simple form
could I not sob? could you not sob? could he not sob? could we not sob? could you not sob? could they not sob?
V-ing form
could I not be sobbing? could you not be sobbing? could he not be sobbing? could we not be sobbing? could you not be sobbing? could they not be sobbing?
Perfect
could I not have sobbed? could you not have sobbed? could he not have sobbed? could we not have sobbed? could you not have sobbed? could they not have sobbed?
V-ing perfect
could I not have been sobbing? could you not have been sobbing? could he not have been sobbing? could we not have been sobbing? could you not have been sobbing? could they not have been sobbing?