must crack
Regular verb: crack - cracked- cracked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must crack
you must crack
he must crack
we must crack
you must crack
they must crack 	I must be cracking
you must be cracking
he must be cracking
we must be cracking
you must be cracking
they must be cracking	I must have cracked
you must have cracked
he must have cracked
we must have cracked
you must have cracked
they must have cracked	I must have been cracking
you must have been cracking
he must have been cracking
we must have been cracking
you must have been cracking
they must have been cracking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must not crack
you must not crack
he must not crack
we must not crack
you must not crack
they must not crack 	I must not be cracking
you must not be cracking
he must not be cracking
we must not be cracking
you must not be cracking
they must not be cracking	I must not have cracked
you must not have cracked
he must not have cracked
we must not have cracked
you must not have cracked
they must not have cracked	I must not have been cracking
you must not have been cracking
he must not have been cracking
we must not have been cracking
you must not have been cracking
they must not have been cracking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I crack?
must you crack?
must he crack?
must we crack?
must you crack?
must they crack? 	must I be cracking?
must you be cracking?
must he be cracking?
must we be cracking?
must you be cracking?
must they be cracking? 	must I have cracked?
must you have cracked?
must he have cracked?
must we have cracked?
must you have cracked?
must they have cracked? 	must I have been cracking?
must you have been cracking?
must he have been cracking?
must we have been cracking?
must you have been cracking?
must they have been cracking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I not crack?
must you not crack?
must he not crack?
must we not crack?
must you not crack?
must they not crack? 	must I not be cracking?
must you not be cracking?
must he not be cracking?
must we not be cracking?
must you not be cracking?
must they not be cracking? 	must I not have cracked?
must you not have cracked?
must he not have cracked?
must we not have cracked?
must you not have cracked?
must they not have cracked? 	must I not have been cracking?
must you not have been cracking?
must he not have been cracking?
must we not have been cracking?
must you not have been cracking?
must they not have been cracking?