must combust
Regular verb: combust - combusted- combusted

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I must combust
you must combust
he must combust
we must combust
you must combust
they must combust 	I must be combusting
you must be combusting
he must be combusting
we must be combusting
you must be combusting
they must be combusting	I must have combusted
you must have combusted
he must have combusted
we must have combusted
you must have combusted
they must have combusted	I must have been combusting
you must have been combusting
he must have been combusting
we must have been combusting
you must have been combusting
they must have been combusting	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I mustn't combust
you mustn't combust
he mustn't combust
we mustn't combust
you mustn't combust
they mustn't combust 	I mustn't be combusting
you mustn't be combusting
he mustn't be combusting
we mustn't be combusting
you mustn't be combusting
they mustn't be combusting	I mustn't have combusted
you mustn't have combusted
he mustn't have combusted
we mustn't have combusted
you mustn't have combusted
they mustn't have combusted	I mustn't have been combusting
you mustn't have been combusting
he mustn't have been combusting
we mustn't have been combusting
you mustn't have been combusting
they mustn't have been combusting	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
must I combust?
must you combust?
must he combust?
must we combust?
must you combust?
must they combust? 	must I be combusting?
must you be combusting?
must he be combusting?
must we be combusting?
must you be combusting?
must they be combusting? 	must I have combusted?
must you have combusted?
must he have combusted?
must we have combusted?
must you have combusted?
must they have combusted? 	must I have been combusting?
must you have been combusting?
must he have been combusting?
must we have been combusting?
must you have been combusting?
must they have been combusting? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
mustn't I combust?
mustn't you combust?
mustn't he combust?
mustn't we combust?
mustn't you combust?
mustn't they combust? 	mustn't I be combusting?
mustn't you be combusting?
mustn't he be combusting?
mustn't we be combusting?
mustn't you be combusting?
mustn't they be combusting? 	mustn't I have combusted?
mustn't you have combusted?
mustn't he have combusted?
mustn't we have combusted?
mustn't you have combusted?
mustn't they have combusted? 	mustn't I have been combusting?
mustn't you have been combusting?
mustn't he have been combusting?
mustn't we have been combusting?
mustn't you have been combusting?
mustn't they have been combusting?