must crackle
Regular verb: crackle - crackled- crackled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must crackle
you must crackle
he must crackle
we must crackle
you must crackle
they must crackle 	I must be crackling
you must be crackling
he must be crackling
we must be crackling
you must be crackling
they must be crackling	I must have crackled
you must have crackled
he must have crackled
we must have crackled
you must have crackled
they must have crackled	I must have been crackling
you must have been crackling
he must have been crackling
we must have been crackling
you must have been crackling
they must have been crackling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't crackle
you mustn't crackle
he mustn't crackle
we mustn't crackle
you mustn't crackle
they mustn't crackle 	I mustn't be crackling
you mustn't be crackling
he mustn't be crackling
we mustn't be crackling
you mustn't be crackling
they mustn't be crackling	I mustn't have crackled
you mustn't have crackled
he mustn't have crackled
we mustn't have crackled
you mustn't have crackled
they mustn't have crackled	I mustn't have been crackling
you mustn't have been crackling
he mustn't have been crackling
we mustn't have been crackling
you mustn't have been crackling
they mustn't have been crackling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I crackle?
must you crackle?
must he crackle?
must we crackle?
must you crackle?
must they crackle? 	must I be crackling?
must you be crackling?
must he be crackling?
must we be crackling?
must you be crackling?
must they be crackling? 	must I have crackled?
must you have crackled?
must he have crackled?
must we have crackled?
must you have crackled?
must they have crackled? 	must I have been crackling?
must you have been crackling?
must he have been crackling?
must we have been crackling?
must you have been crackling?
must they have been crackling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I crackle?
mustn't you crackle?
mustn't he crackle?
mustn't we crackle?
mustn't you crackle?
mustn't they crackle? 	mustn't I be crackling?
mustn't you be crackling?
mustn't he be crackling?
mustn't we be crackling?
mustn't you be crackling?
mustn't they be crackling? 	mustn't I have crackled?
mustn't you have crackled?
mustn't he have crackled?
mustn't we have crackled?
mustn't you have crackled?
mustn't they have crackled? 	mustn't I have been crackling?
mustn't you have been crackling?
mustn't he have been crackling?
mustn't we have been crackling?
mustn't you have been crackling?
mustn't they have been crackling?