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