I can crack you can crack he can crack we can crack you can crack they can crack
V-ing form
I can be cracking you can be cracking he can be cracking we can be cracking you can be cracking they can be cracking
Perfect
I can have cracked you can have cracked he can have cracked we can have cracked you can have cracked they can have cracked
V-ing perfect
I can have been cracking you can have been cracking he can have been cracking we can have been cracking you can have been cracking they can have been cracking
Negation
Simple form
I can't crack you can't crack he can't crack we can't crack you can't crack they can't crack
V-ing form
I can't be cracking you can't be cracking he can't be cracking we can't be cracking you can't be cracking they can't be cracking
Perfect
I can't have cracked you can't have cracked he can't have cracked we can't have cracked you can't have cracked they can't have cracked
V-ing perfect
I can't have been cracking you can't have been cracking he can't have been cracking we can't have been cracking you can't have been cracking they can't have been cracking
Interrogative form
Simple form
can I crack? can you crack? can he crack? can we crack? can you crack? can they crack?
V-ing form
can I be cracking? can you be cracking? can he be cracking? can we be cracking? can you be cracking? can they be cracking?
Perfect
can I have cracked? can you have cracked? can he have cracked? can we have cracked? can you have cracked? can they have cracked?
V-ing perfect
can I have been cracking? can you have been cracking? can he have been cracking? can we have been cracking? can you have been cracking? can they have been cracking?
Interro-negative form
Simple form
can't I crack? can't you crack? can't he crack? can't we crack? can't you crack? can't they crack?
V-ing form
can't I be cracking? can't you be cracking? can't he be cracking? can't we be cracking? can't you be cracking? can't they be cracking?
Perfect
can't I have cracked? can't you have cracked? can't he have cracked? can't we have cracked? can't you have cracked? can't they have cracked?
V-ing perfect
can't I have been cracking? can't you have been cracking? can't he have been cracking? can't we have been cracking? can't you have been cracking? can't they have been cracking?