I could crack you could crack she could crack we could crack you could crack they could crack
V-ing form
I could be cracking you could be cracking she could be cracking we could be cracking you could be cracking they could be cracking
Perfect
I could have cracked you could have cracked she could have cracked we could have cracked you could have cracked they could have cracked
V-ing perfect
I could have been cracking you could have been cracking she could have been cracking we could have been cracking you could have been cracking they could have been cracking
Negation
Simple form
I could not crack you could not crack she could not crack we could not crack you could not crack they could not crack
V-ing form
I could not be cracking you could not be cracking she could not be cracking we could not be cracking you could not be cracking they could not be cracking
Perfect
I could not have cracked you could not have cracked she could not have cracked we could not have cracked you could not have cracked they could not have cracked
V-ing perfect
I could not have been cracking you could not have been cracking she could not have been cracking we could not have been cracking you could not have been cracking they could not have been cracking
Interrogative form
Simple form
could I crack? could you crack? could she crack? could we crack? could you crack? could they crack?
V-ing form
could I be cracking? could you be cracking? could she be cracking? could we be cracking? could you be cracking? could they be cracking?
Perfect
could I have cracked? could you have cracked? could she have cracked? could we have cracked? could you have cracked? could they have cracked?
V-ing perfect
could I have been cracking? could you have been cracking? could she have been cracking? could we have been cracking? could you have been cracking? could they have been cracking?
Interro-negative form
Simple form
could I not crack? could you not crack? could she not crack? could we not crack? could you not crack? could they not crack?
V-ing form
could I not be cracking? could you not be cracking? could she not be cracking? could we not be cracking? could you not be cracking? could they not be cracking?
Perfect
could I not have cracked? could you not have cracked? could she not have cracked? could we not have cracked? could you not have cracked? could they not have cracked?
V-ing perfect
could I not have been cracking? could you not have been cracking? could she not have been cracking? could we not have been cracking? could you not have been cracking? could they not have been cracking?